The Transit of Venus Enterprise in Victorian Britain

THE TRANSIT OF VENUS ENTERPRISE IN VICTORIAN BRITAIN

SCIENCE AND CULTURE IN THE NINETEENTH CENTURY Series Editor: Bernard Lightman

TITLES IN THIS SERIES Styles of Reasoning in the British Life Sciences: Shared Assumptions, 1820–1858 James Elwick Recreating Newton: Newtonian Biography and the Making of NineteenthCentury History of Science Rebekah Higgitt FORTHCOMING TITLES Medicine and Modernism: A Biography of Sir Henry Head L. S. Jacyna Science and Eccentricity: Collecting, Writing and Performing Science for Early Nineteenth-Century Audiences Victoria Carroll

www.pickeringchatto.com/scienceculture

THE TRANSIT OF VENUS ENTERPRISE IN VICTORIAN BRITAIN

BY

Jessica Ratcliff

london PICKERING & CHATTO 2008

Published by Pickering & Chatto (Publishers) Limited 21 Bloomsbury Way, London WC1A 2TH 2252 Ridge Road, Brookfield, Vermont 05036-9704, USA www.pickeringchatto.com All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without prior permission of the publisher. © Pickering & Chatto (Publishers) Limited 2008 © Jessica Ratcliff 2008 British Library Cataloguing in Publictattion Data Ratcliff, Jessica The transit of Venus enterprise in Victorian Britain. – (Science and culture in nineteenth-century Britain) 1. Science – Great Britain – History – 19th century 2. Venus (Planet) – Transit – 1874 3. Venus (Planet) – Transit – 1882 I. Title 523.9’2’09034 ISBN-13: 9781851965410

∞

This publication is printed on acid-free paper that conforms to the American National Standard for the Permanence of Paper for Printed Library Materials. Typeset by Pickering & Chatto (Publishers) Limited Printed in the United Kingdom at the University Press, Cambridge

CONTENTS

Acknowledgements List of Illustrations Introduction Summary of the Chapters 1 The Precedent: Transit of Venus Expeditions in 1761 and 1769 The Historical Precedent 2 Big Science in Britain c. 1815–70 The Magnetic Crusades: The Bigger Science Between the Two Transits Admiralty Science and the Reform Movement Airy’s Greenwich and its Place in the Historiography 3 Noble Science, Noble Nation: The Establishment of Transit Programmes in Britain and Abroad Edward Stone, the Black Drop Effect and the Transit of Mercury in 1868 The Transit Proposal in Parliament The International Picture: Transit Programmes Abroad Situating the Observation Stations Britain’s Scientific Honour, the Press and the Airy-Proctor Debate 4 Inside Greenwich: The Preparations for 1874 Warren De La Rue and the Photographic Plan Precision Astronomical Photography in the Wet-Plate Era Programme Design as a National Product The Telescopic Plan: Modelling the Transit of Venus Artificial Black Drop Experiments Training the Observers Model Training versus Personal Equation Measures The International Melee 5 The Expeditions Establishing the Observation Stations: The Case of Cairo Environment, Local Time and Latitude: Work Routines at the Stations

vii ix 1 6 9 13 21 22 25 29 35 37 41 45 46 49 57 60 66 74 77 80 82 84 86 89 94 99

Longitude Experiments Lindsay and Gill’s Chronometric Trials Browne’s Experiment in Submarine Telegraphy The Day of the Transit: 8–9 December 1874 The Transit of Venus Observed in Cairo Worldwide Spectacle: The Day of the Transit in the Press 6 The Outcome Airy’s International Proposal for Reducing the Observations Calculating Parallax in 1874 versus 1769 The Plan to Measure the Photographs The Mist of Words Financial Crisis ‘Casting’ Phases and ‘Doctoring’ Results Deciding that Photography had Failed The Official Publication and the Retirement of the Astronomer Royal Outcomes and Results Beyond Greenwich Conclusion Measurement in Late Victorian Science National Science, Growth and Progress Epilogue: The Transit of 1882 Change of Leadership and Loss of Resources The Question of International Cooperation The New Instructions to Observers The Longitude Work and the Loss of Admiralty Patronage The Expeditions The Outcome The Transit Enterprise, International Cooperation and Precision Astronomical Photography

102 104 105 108 111 114 119 121 124 125 128 130 133 138 140 143 147 147 150 153 155 158 159 162 164 166

Notes Works Cited Index

173 197 213

168

ACKNOWLEDGEMENTS

I would like to thank Stephen Johnston, first for suggesting the transits of Venus as a dissertation topic, second, for being so generous with his time, ideas and editorial talents, and third, for enduring years of transit of Venus meetings at the King’s Arms. Of course all mistakes, omissions and weak arguments are my fault alone. Thanks also to Jim Bennett and Jon Agar who read this work in dissertation form and gave thoughtful suggestions, criticisms and corrections. I am particularly indebted to Robert Smith for his interest in this work and for his crucial input on how to turn the dissertation into a book. I would also like to thank the series editor, Bernard Lightman, and the anonymous referees, whose comments on the initial monograph manuscript were immensely helpful. For additional feedback on earlier versions of this work, I would also like to thank: Jon Bateson, Terje Brundtland, Peter Dear, Katie Finch, Robert Fox, Minsoo Kang, Kevin Lambert, Faidra Papanelopoulou, Huw Price, Pedro Ruiz-Castell, Robert Schombs and Suman Seth. For her editorial help, I would like to thank Julie Wilson at Pickering & Chatto. And very special thanks are due to my brother Jason Ratcliff and my husband Nico Silins for taking on the task of proofreading the final version of this work. I would like to acknowledge the archivists and curators who have aided my research. Thanks especially to Adam Perkins and the Cambridge University Library; Emily Winterburn and Rob West and the Royal Observatory, Greenwich; Mark Steadman at the Porthcurno Museum; Colin Vincent and Simon Berry at PPARC; Karen Moran at the Royal Observatory, Edinburgh; Devon Pyle-Vowles at the Adler Planetarium; and Peter Hingley at the Royal Astronomical Society Library. I would also like to acknowledge the help of other historians of the transits of Venus with whom I have corresponded, especially David Aubin, Jimena Canales, Allan Chapman, Michael Chauvin, Steve Dick, Hilmar Duerbeck, Leititia Maison, William Sheehan and Richard Staley. Finally, I would like to thank my parents, Roger Ratcliff and Donna Young, and John and Barbara Rossi.

vii

LIST OF ILLUSTRATIONS AND TABLES

Figure 1. Figure 2. Figure 3.

Figure 16. Figure 17.

The transit of Venus method of measuring the sun’s distance 11 The black drop as drawn by observers in 1769 37 Map showing the regions in the world where egress, ingress and the entire transit were visible 42 The frontispiece to the bound annual of Punch, 1874 55 One of the photoheliographs set up in its custom-built observation hut during a trial run at Greenwich 65 ‘Transit of Venus – Model used for Practice at Greenwich Observatory’ 78 One of the five training models constructed for each station, here set up at Honolulu 79 An illustration of the difference between the paths Venus will appear to take across the sun, depending on how far north or south the observer is on Earth 81 Expedition members gathered at Greenwich prior to the transit 89 ‘Plan of the Environs of Cairo showing the position of Captain Orde Browne’s Encampment on Jebel Jeushi, Mokattam Range’ 95 Front embossing for the hardback binding of the year 1874 for Illustrated London News 96 ‘Landing stores on the beach – Rodriguez’ 97 A printed glass plate photograph of the transit of Venus from the 1874 British programme 120 Six of the original 1874 transit of Venus glass plate negatives 120 A page of the final illustrations for the observations at Cairo, based on observer drawings of the appearances at contact 122 ‘Success of Stations, as reported in Telegrams etc.’ 137 The back plate to the bound annual of Punch, 1874 147

Table 1.

Transit of Venus 1874: British Stations and Personnel

Figure 4. Figure 5. Figure 6. Figure 7. Figure 8.

Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15.

ix

117

The scientific reports from all those observers will be recondite and abstruse; but in ten or twenty lines of the next edition of a school geography all the results obtained by a vast expenditure of money, energy, and skill will be clearly stated. Then, on summers’ evenings or in early morning, as the almanac will guide them, our children and their children’s children through a hundred years will be satisfied to look upon the brilliant radiance of the lovliest of all the stars – not dreaming that stern scholars of many nations used it as a bead upon a transit instrument to measure how far we live away from the sun. The Irish Times (Dublin), 9 December 1874

INTRODUCTION

This characteristic of modern experiments – that they consist principally of measurements – is so prominent, that the opinion seems to have got abroad that, in a few years, all the great physical constants will have been approximately estimated, and that the only occupation which will then be left to men of science will be to carry on these measurements to another place of decimals … James Clerk Maxwell (1871)1 Each observer went out ticketed with his ‘personal equation’, his senses drilled into a species of martial discipline, his powers absorbed, so far as possible, in the action of a cosmopolitan observing machine. Agnes Clerke (1902)2 The astronomers who are to-day to make their observations have all gone through the preliminary process of what is technically known as correcting their personal equation … What a gain to political life in practice it would be if we could only correct the personal equation of those who think, write, speak, and act in the sphere of politics! Suppose, among our members of Parliament, we could exactly measure and allow for the inordinate vanity of one, the litigious querulousness of another, the professional bias of a third, the hereditary, national or sectarian prejudices of a fourth … Sydney Morning Herald, 9 December 1874

On 9 December 1874, in Sydney, New South Wales, a rare transit of Venus happened to coincide with a round of important local elections. In the Sydney Morning Herald for that day, set among articles about ship arrivals, a smoking volcano in the Torres Strait and commodities quotations from Singapore (nutmeg, mace, pepper, pearl sago, tapioca, rice, coffee, cigars, etc.), there is an article entitled ‘Science and Politics’. The article sets out to contrast these two ‘very different phases of human action’. On that morning, at the observatory on Flagstaff Hill, astronomers were straining to time with the utmost precision the passage of the silhouette of Venus as it crawled across the surface of the sun. Sydney was just one of hundreds of spots on the globe where similar observations were being made on that day. The goal was to measure the distance between the earth and the sun to the highest possible degree of precision permitted by modern methods of measurement. Meanwhile, on the same day, in the world of Sydney politics, the hustings at Hyde Park was a spectacle of ‘passion, excitement, mis–1–

2

The Transit of Venus

representation, manouvering, and questionable agencies’. In the Sydney Morning Herald, the practice of science – with its focus on dispassionate observation – was drawn in remarkable contrast to the practice of politics, ‘which depends on the coloured and distorted lens of party spirit’. There is some irony in how the Sydney Morning Herald article uses the case of the transit as an opportunity to meditate on the separation of science and politics. In fact, the worldwide transit enterprise of 1874 was thoroughly shaped by national political ideologies. Five major world powers conducted separate transit of Venus programmes. Expeditions from Britain, France, Germany, Russia and the United States each set out with the same goal of measuring the sun’s distance. On this unusually crowded international stage, participants and commentators alike approached the question of the sun’s distance through the ‘colored and distorted lens’ of nationalism, and the whole enterprise would owe much of its size and shape to the air of international competition that gathered around it. Nationalism with respect to science was commonplace in nineteenthcentury Britain. It was also curiously cosmopolitan, mixing national pride in scientific achievements with a view of science as a pursuit that knows no political borders. So, for example, while the press in Britain often described the British programme with patriotic enthusiasm (an attitude shared by many astronomers and politicians), at the same time the press assumed that the astronomers of different countries were collaborating much more closely than in fact they were. Similarly, while readers were regaled with the historical achievements of British science, they were also reminded of the universal benefit certain to be brought by such ambitious scientific pursuits. In the case of the transit of Venus, each participating country acted according to its own interests, and yet the underlying sense of the universal character of science remained. As the Sydney Morning Herald put it, the ‘practical applications’ of science ‘are rendering the greatest service to human wellbeing’. Even the Admiralty saw itself as contributing to ‘the common stock of accurate science’.3 Science, according to this standard ideology, was essentially cosmopolitan. At the same time, however, to be a cosmopolitan figure on the international stage one must have a strong individual character. In the case of the transit of Venus, each participating country acted in the interest of its own national scientific honour. That intermingled ideology is expressed in Agnes Clerke’s summation of the enterprise: ‘Every country which had a reputation to keep or to gain for scientific zeal was forward to co-operate in the great cosmopolitan enterprise of the transit’.4 That intermixture of nationalism and internationalism with respect to science was fully on display at the gargantuan international exhibitions of the period. The Great Exhibition of 1851, for example, according to the organizers and the promoters, encouraged universal improvement through an international

Introduction

3

exchange in ideas. That exchange, however, would take place under cover of direct competition among nations for prestige, medals and honours. In the process, national types were promoted; the notion of distinctive national styles was reinforced. Each country’s own patriotism was fluffed and buffed for exposition. Britain celebrated its own national style. The characteristics of other countries were sometimes admired, and sometimes they were ridiculed. But the everpresent overarching idea was that, through all of that competition, civilization as a whole was to benefit.5 At the same time, however, this was a British version of internationalism. In the liberal politics to which the Exhibition’s foundation was tied, that version supported a form of global market that Britain was set to dominate. Some historians have argued that nationalism as an ideology only first emerged in the late nineteenth century. An influential contemporary examination of the idea was laid out by the controversial French theorist Ernest Renan in his famous 1882 essay ‘What is a Nation?’. Renan’s definition of a nation rests on a similarly cosmopolitan nationalism: ‘Through their various and often opposed powers, nations participate in the common work of civilization; each sounds a note in the great concert of humanity …’.6 Renan’s understanding of nationality rested upon the shared history and experience of a nation’s members: ‘More valuable by far than common customs posts and frontiers conforming to strategic ideas is the fact of sharing, in the past, a glorious heritage and regrets, and of having, in the future, [a shared] programme to put into effect, or the fact of having suffered, enjoyed, and hoped together’.7 Science, like literature and the arts, sometimes figures strongly in communal perceptions of history; Newton is like an English founding father. The transit enterprise also drew much of its political significance from history. In the nineteenth century, transits of Venus were already written into the history books and were already a great source national historic pride. This is because the previous transit of Venus, which had occurred in 1769, had been the occasion for Captain James Cook’s first travels to the South Pacific, and his first exploration of Australasian lands. In the mid-nineteenth century Cook was probably the most famous explorer in England, and his observations of the transit of Venus in Tahiti were legendary (see for example the epigraph to Chapter 1). In the build-up to the transit of 1874, that sentimentality would influence everything from funding decisions to the blooming of the patriotic rhetoric in the press. And its influence was not just on a public level. For the astronomers involved, as we will see, the history of the previous transit would be enormously important. According to the Sydney Morning Herald article, the important point about the contrasting methodologies of science and politics has to do with progress. Because politicians cannot be made unbiased and impersonal by the application of anything like a ‘personal equation’, politics will never see anything akin to the

4

The Transit of Venus

remarkable progress enjoyed by science over the previous three centuries. On the subject of progress in science, the article is exuberant, an attitude that was not at all unusual for the late nineteenth century. Scientific progress was then a given; it was a hallmark of the era. And, with respect to the physical sciences, progress was was characterized by precision measurement: the increasingly precise measurements of an increasingly broad range of natural phenomena. In the middle of the nineteenth century the Prussian naturalist Alexander von Humboldt famously predicted that astronomy was reaching its end, having nearly fulfilled its mission of accurately measuring the heavens.8 James Clerk Maxwell, though not endorsing that view, acknowledged the widespread perception that ‘the only occupation which will then be left to men of science will be to carry on these measurements to another place of decimals …’.9 The transit of Venus enterprise fits the Humboltdian mould of nineteenth-century science like a glove. Its goal was to measure the mean distance to the sun – the value of which is an important standard of measure in astronomy and physics – to a new degree of precision. This depended upon capturing a particular form of extremely precise observations. In the popular press, the degree of precision required of the observations was often highlighted by dramatic analogies, such as when the Graphic of London conveyed the difficulty of the observations by explaining that ‘It is, as The Times put it the other day, as if a man standing on the Victoria Tower should endeavour to ascertain the distance of the Albert Memorial in Hyde Park by viewing it successively from the two ends of a twelve-inch ruler’.10 The Farmers’ Almanac, a popular Victorian periodical, put it this way: Suppose a human hair to be set up a distance of half a mile from the observer, and that the true line of sight passed on the right-hand side of that hair. Now, if by any mischance the observer should observe the left-hand side of the hair instead of the right, that error in calculating the Sun’s distance would make a difference of about a million of miles. Consequently, to obtain the true distance of the Sun within a half million of miles, it is necessary to determine the true line of sight within the breadth of a hair viewed at the distance of a mile.11

Astronomers and the public alike were awed by this measurement challenge. It was a new hurdle for modern science to overcome. On 8–9 December, throughout the collective empire of European nations, scientific progress was celebrated in coverage of the 1874 transit of Venus. But as it turned out, the observations made on that day, a culmination of more than five years of preparation, would never yield an improved measure of the sun’s distance. The transit of Venus enterprise would turn out to be an instance of Humboltdian science that failed to clear the hurdle of precision that had been set for it. A few decades later the transit of Venus was to be remembered most of all (when it was to be remem-

Introduction

5

bered at all) for the outstanding lack of progress achieved.12 In this respect the transit enterprise has something in common with the small colonial wars that Britain lost during the nineteenth century. In a century usually characterized as being ‘without major wars’ those minor ones, especially the losing ones, have been leached of historical significance.13 The same goes for nineteenth-century science; in a century usually characterized by unprecedented scientific progress, many of the failed experiments, discounted theories and unsuccessful inventions have receded out of sight. A number of books on the history of the transits of Venus have been published, but in all but one case the focus is on the transit programmes of the eighteenth century, including the voyage of James Cook.14 With a few important exceptions, the subject of Britain’s nineteenth-century transit enterprise has not been covered in any detail by historians.15 This is true despite the surge of interest in their histories that came with the return of the transit of Venus in June 2004. As for the transit programmes outside Britain, a significant amount of work has recently been done on the transit programmes of the United States, France, Germany and Russia. That scholarship has been essential to the writing of this book, enabling crucial comparisons to be made between the British programme and those of other countries.16 But even with this material to rely on, the comparative dimension of this book is not as thorough as it could have been. Sprawling as it is, this book only examines one facet of a much bigger story. This book is the first detailed narrative of the British transit enterprise in 1874 and 1882 (with the focus on the much larger effort of 1874). The intention, however, is that the value of this history will reach beyond historiographical hole-filling. The hope is also that the narrative will draw attention to the following more general points: 1. That the practices of precision measurement in late Victorian astronomy contain interesting historically specific characteristics, and that those practices reflect an appreciation of the problems and limitations of measurement. 2. That the Admiralty played a key role in shaping the culture and direction of Victorian science. 3. That both ‘big science’ and the (often very closely related) role of science in nationalistic ideology have historical roots extending well into the nineteenth century. 4. That growth in science should be understood separately from progress in science, and that failure in science deserves more attention than it has so far received.

6

The Transit of Venus

Summary of the Chapters The book begins with the transit of Venus expeditions of 1761 and 1769. These eighteenth-century transits are linked to those of the nineteenth century in important ways. The transit enterprise of 1874 was a repeat of the nearly identical efforts made in 1761 and 1769. The nineteenth-century politicians, astronomers and journalists saw the 1874 programme as a modernized re-enactment – complete with photography, steam travel and telegraphy – of the historic expeditions. At the same time, the reports from the 1760s would become absolutely central to the preparations for the transit of 1874. So, even while the Victorian astronomers rejected some of the methods used in the 1760s (such as reflecting telescopes for precision observation), they also depended heavily on the results of those methods. In fact the two programmes, although over a century apart, might best be seen as part of a single astronomical enterprise, albeit one that was forced to proceed according to the cosmic timescale of planetary alignments. Chapter 2 describes the institutional and cultural setting out of which the enterprise of 1874 would emerge. On one level, the scale and cultural significance of the transit must be understood with respect to its status as a ‘pure’ or ‘abstract’ astronomical pursuit. This is closely related to the symbolic value conferred on positional astronomy generally, and on Greenwich in particular, by weight of tradition. The character and operation of Victorian Greenwich under the Astronomer Royal George Biddell Airy, a crucial influence on the development of the programme, will be introduced here. On another level, the transit must be understood as a brand of Victorian military science. In general the ‘big science’ of the nineteenth century was Admiralty science. The transit enterprise is in company with and shares many characteristics of the other ‘big science’ ventures of the time, such as the Magnetic Crusades and the oceanographic expedition of HMS Challenger, both of which are also described in this chapter. Many historians (following the claims of Victorian actors) have argued that state funding of science was especially and even strangely weak in the nineteenth century. But, as will be discussed here, when these large-scale Admiralty-funded projects are also taken into consideration, the picture of government science funding at the time becomes more complex. Chapters 3 through 7 unravel the narrative of the enterprise surrounding the transit of Venus in 1874. Chapter 3 charts the rise of the transit programme in Britain. It began as just one option among many for measuring the sun’s distance proposed by the Astronomer Royal in 1857, but by 1869 it had gained near-universal support among astronomers. This was followed by official parliamentary support. Crucially, during that period, astronomers would begin to re-examine the reports from 1761 and 1769 with the aim of uncovering and correcting suspected errors in the old data. A transit of Mercury in 1868 became an occasion to test

Introduction

7

newly-developed theories about how to measure the transit of Venus. And finally, a very public debate between the astronomy writer Richard Anthony Proctor and George Airy brought the subject of the transit into the popular press, where it quickly came to represent a test of national scientific honour. Chapter 4 investigates the preparations at Greenwich in the build-up to 1874. During the four years between the establishment of the programme and the day of the transit of Venus, Greenwich was the site of time constrained research into a host of unknowns surrounding issues of methodology. This involved investigations into subjects ranging from conductivity in submarine telegraphic wires to the shape of the sun to the properties of photographic emulsions. In the process, Greenwich came to operate more like the private astrophysical observatories of the Victorian grand amateurs, and indeed Airy would enlist the help of some of the most prominent amateur astronomers of the time. Warren De La Rue became the unofficial director of the experimental and controversial photographic plan. By and large the rest of the staff was drawn from the military. George Lyon Tupman, a captain in the Royal Marine Artillery, oversaw all aspects of the preparation. Much of the planning and training was executed with the help of a mechanical model of the transit of Venus. This simulated transit of Venus came to play a crucial role during the preparations, as instruments and observers were calibrated on the model according to a very delicate and specific observational procedure. Internationally, there was very little agreement on methods for observing and recording the transit, and each country ended up with an idiosyncratic plan. Chapter 5 turns to the expeditions. On 8–9 December, the transit of Venus would be front-page news throughout Europe, North America and the many parts of the globe where there was European-language press. In the coverage in the press, emphasis now shifted from inter-European comparisons to straightforwardly jingoistic celebrations of the expeditions as part of the imperial fabric of the time. In this chapter, the expeditions are explored from the perspective given by the letters and reports of the expedition members. The station at Cairo is taken as a case study, but material is also drawn from the other British expeditions. The chapter follows not only the social and political dynamic of the camp as it was established in the Cairo area, but also details the work routines at the station. This includes the important auxiliary work of finding the latitude and longitude of the stations. Here too, the transit became an occasion to experiment with new methods and to refine the capabilities of old ones – most importantly a new attempt at long-distance telegraphic longitude determination. And finally, at the centre of the entire enterprise are the few hours of the transit of Venus on 8–9 December. Chapter 6 traces the outcome of the 1874 enterprise. Over the next five years the staff at Greenwich engaged in a protracted struggle with some of the

8

The Transit of Venus

most imprecise, vague, and problematic data that Greenwich had ever produced. The photographic plates and the observational reports each presented their own challenges, but, essentially, the problem with both forms of data was the same: no matter what analytical tools were used, no certain result could be drawn. Some of the debates about transit methods, especially those concerning the photographic methods, continued to simmer after the transit, finally reaching a resolution towards the end of the 1870s. The unexpected implications of using the simulation transit of Venus also became apparent at this time. During this period, the government’s support of the transit programme also declined sharply, and the calculations proceeded under much greater financial pressure than had the preparations or the expeditions. These and other factors combined to hasten a slowly unfolding consensus that the enterprise had been a failure. The Epilogue covers the transit of Venus programme in 1882. That effort, not surprisingly, was made with less energy, resource and ambition. The preparations only began in late 1880, there were fewer expeditions, and the results were churned out within a relatively short period. But the 1882 programme was not merely a shrunken version of the 1874 enterprise. Different people and institutions were involved, and they employed new modes of management and a revised approach to the challenge of measuring the transit. The very different nature of the transit programme for 1882 underlines certain aspects of both the general failure and certain auxiliary successes of the 1874 enterprise. Some of those changes – especially the more concerted effort at international organization – are evidence of larger, more sustained developments in late nineteenth-century astronomy. Others, like the rejection of photography in 1882, run contrary to the historical trends of the period.

1 THE PRECEDENT: TRANSIT OF VENUS EXPEDITIONS IN 1761 AND 1769

The former Transits in 1761 and 1769, bring up before us the delightful voyages of Captain Cook and all that was recorded by Dr Banks and Dr Solander, and how, when in youth we first pored over the story in Hawkesworth’s voyages we longed to fly to Otahetie and swim in the warm seas there. But all that is left to this generation, and the longest lives of those in the second after us, is to record the dry details of astronomers, and look at the negatives of photographers who were nervously anxious yesterday in the sunshine while the sleet and rain were falling here, and the north-east wind was blowing. The Irish Times (Dublin), 9 December 1874

It was a sunny morning in Jamestown, St Helena, on 7 November 1677. Given its extreme remoteness – St Helena is a tip of volcanic land in the South Atlantic Ocean equidistant between South America and Africa – Jamestown was surprisingly urbane in the 1670s. For over a hundred years, the port had been a supply outpost of the British East India Company and, before that, was used by the Portuguese. Far south of the equator, usually cloudless, formerly uninhabited and now English-civilized, St Helena was a perfect place to observe the southern night sky. In November 1677 one aspiring astronomer, a well-off twenty-oneyear-old Englishman named Edmond Halley, was here to map the southern stars and to observe a relatively rare transit of Mercury. That is what he was doing on the sunny morning of 7 November, at around 9 o’clock. Halley had his telescope (fitted with a smoked-glass filter) pointed at the sun. A small black notch appeared at the outer edge of the solar disc, creeping into the limb of the sun. The notch grew into a small black semicircle. It was the silhouette of the planet Mercury, cast onto the sun as seen from Earth. Halley watched with special interest as, at approximately 9.30, the shadow’s entire shape, a circular silhouette, finally completed itself. The circular silhouette closed in an instant, when what Halley would later describe as a ‘lucid line of light’ appeared and reconnected the outer limb of the sun. Thus the silhouette of Mercury began its transit. –9–

10

The Transit of Venus

All of these details are recalled by Halley much later on, after he had risen to the rank of Astronomer Royal at Greenwich. He recounted the experience of observing a transit of Mercury in a 1716 paper in the Philosophical Transactions. The point of the paper was to describe a plan for measuring the sun’s distance using a transit of Venus, which would provide better circumstances than a Mercury transit.1 In this paper, Halley recalled that it was after observing that moment when the shadow of the planet fully entered the sun, marked by the appearance of a thread of light at the shadow’s outer edge, that he was struck with the idea of measuring the distance to the sun using observations of planetary transits. Benjamin Martin, in a 1761 reprint and commentary on Halley’s original Latin paper, provides a memorable account of Halley’s crucial observation: [Halley thus] discovered the precise Quantity of Time the whole Body of Mercury had then appeared within the Sun’s Disk, and that without an Error of one single Second of Time; for the Thread of Solar Light, interceded between the obscure Limb of the Planet, and the bright Limb of the Sun, though exceeding slender, affected his Sight, and in the Twinkling of an Eye both the Indenture made on the Sun’s Limb by Mercury entering into it vanished, and that made by his going off appeared. Upon observing this, he immediately concluded, that the Sun’s Parallax might be duly determined by such Observations, if Mercury, being nearer the Earth had a greater Parallax when seen from the Sun.’2

Halley’s plan depended crucially upon the nature of this observation. That is, it depended upon observers being able to time the duration of the transit, and it was that ‘Thread of Solar Light’, which instantaneously formed or broke, that provided a discrete marker of the beginning (or end, if it is disappearing). If, as Halley reasoned, there had been someone also observing the transit of Mercury from a position much farther north or south than himself, then that observer would have seen the line of light appear at a slightly different absolute time. Most importantly, the difference in the timing of the transit as recorded by two distant observers could be used to calculate the sun’s distance, or solar parallax (as it was then often called; see Figure 1).3 Halley asserted: ‘I know by my own experience [the beginning and end of the transit] may be measurable to within one second of time’.4 If such precise observations were obtained, then Halley’s method could, in theory, provide a measure of the sun’s distance to within 100,000 miles. In the 1670s, calculations of the sun’s distance ranged enormously from 41 to 87 million miles.5 It is also at the centre of this story. The rest of the events covered in this book can be summarized as follows: for the next 200 years, hundreds of astronomers sought to observe and measure that line of light to within the one-second degree of precision that Halley had predicted would be possible. This pursuit generated

The Precedent

11

some of the largest astronomical enterprises of the eighteenth and nineteenth centuries. Transits of Venus are short and rare. They occur in roughly the following pattern: 105 years – 8 years – 120 years – 8 years – 105 years, etc. Each lasts about four hours. When Halley published his method, the most recent transit of Venus had been in 1639, observed only (on record) by Jeremiah Horrox, a young schoolteacher living in Lancashire. The next transits, in 1761 and 1769, would be observed by many hundreds around the world, most of them hoping to contribute to a new measure of the sun’s distance. The history of these eighteenth-century efforts has been covered in detail by Harry Woolf and others.6 The eighteenth-century transits are important to the story of the nineteenthcentury transits for two reasons. First, in the nineteenth century, the transit enterprise was clearly regarded as a repeat of the attempts made in the 1760s. For all involved, including the politicians, astronomers and journalists, the Victorian effort was a modern re-enactment of the Georgian effort, complete with the improved methods and technologies, such as photography, steam travel and telegraphy, that so distinguished their era. The self-regard of the Victorian transit participants as an exercise in modernity or progress, or perhaps as a duty to the history of British science, may even explain to some degree the sizeable inter-

Figure 1. The transit of Venus method of measuring the sun’s distance. From G. Forbes, The Transit of Venus, Nature Series (London: Macmillan and Co., 1874). An observer at S would see Venus cross the sun along DF, while an observer at N would see Venus cross the sun along AC. According to Halley’s method, the solar parallax would be calculated from comparing the lengths of DF and AC to find their difference. In order to find those lengths, observers at N and S would have to carefully time the duration of the transit as seen from their stations. Another method, known as Delisle’s method, compares the absolute times at which the transit either began (at ingress) or ended (at egress), as seen from N and S. In this method, observers at N and S would both record the local time of either ingress or egress, and these times, with an accurate knowledge of the longitude of the station, would be converted to an absolute time such as Greenwich Mean Time. Because an observer at N would see Venus cross the sun at AC, and since AC is closer to the centre of the sun, ingress would happen earlier (‘ingress accelerated by parallax’) than it would for an observer at S (‘ingress retarded by parallax’). Likewise, egress would happen later for an observer at N (‘egress retarded by parallax’) than it would for an observer at S (‘egress accelerated by parallax’). The solar parallax can then be computed by finding the difference in time between, for example, ingress accelerated by parallax and ingress retarded by parallax.

12

The Transit of Venus

est in the Victorian effort. A brief look at the character of the eighteenth-century enterprise will thus help situate the relative ‘progress’ and ‘modernity’ – both real and imagined, both from the perspective of the nineteenth century and of the twenty-first – of the 1874 effort. Second, the reports from the 1760s would become absolutely central to the preparations for the transit of 1874 because they were the only available descriptions of the phenomena. Although Victorian astronomers looked down upon some of the methods used in the 1760s, they depended heavily on the results of those methods in the preparations for 1874. The observation reports of the 1760s were combed through again and again for clues about what to expect at contact. The relation between the two efforts is similar to that between any experiment and a later retrial of the same. In that way, the transits of the 1760s and those of the 1870s and 1880s might best be seen not as separate research programmes but rather as part of a single astronomical enterprise, albeit one that was forced to proceed according to the cosmic timescale of planetary alignments. Along with having one eye fixed on the past, the Victorian transit participants also had one eye fixed on the future. After 1882, the next transit would be in 2004. George Airy justified the enterprise in part with the prediction that ‘the future astronomical public will not be satisfied unless all practical use is made of the transits of Venus of 1874 and 1882’.7 Many commentators waxed poetical on the subject, especially when imagining what future astronomers would make of their efforts. Speaking just before the transit of 1882, William Harkness, a key organizer of the United States programmes, put it like this: We are now on the eve of the second transit of a pair, after which there will be no other till the twenty-first century of our era has dawned upon the Earth, and the June flowers are blooming in 2004. When the last transit season occurred the intellectual world was awakening from the slumber of ages, and that wondrous scientific activity which has led to our present advanced knowledge was just beginning. What will be the state of science when the next transit season arrives God only knows. Not even our children’s children will live to take part in the astronomy of that day.8

Here the weight of history – both the desire to improve on the previous attempts and the desire to do well in the eyes of the future – will at times seem to give a special emotionally-derived momentum to the entire transit of Venus enterprise.

The Precedent

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The Historical Precedent In 1874, the political rhetoric surrounding the transit of Venus in Britain often rested on a certain pride in England’s prominent role in the history of attempts to observe the transit of Venus. In reality, however, England had been much less active than France in the first attempt to bring Halley’s method to completion. Halley died in 1741. A decade later, his plan was revived and revised by Joseph-Nicholas Delisle, a court astronomer in St Petersburg. Delisle began by working out some of the practicalities of Halley’s method. In 1753 there was to be a transit of Mercury, and despite Halley’s belief that the method would be usable only during a Venus transit, Delisle proposed to perform a trial of the method using Mercury’s transit. This would require a coordination of widely dispersed observations. Delisle succeeded in distributing his plan surprisingly widely throughout astronomical communities in Europe and America. His detailed instructions for observation were transmitted by mail along an interwoven network of private correspondence and publication.9 The 1753 transit of Mercury was widely observed. The results, however, did not support a new calculation of solar parallax. During the same period, other methods of measuring the sun’s distance were actively being pursued. Nicolas Louis de la Caille was on an expedition to the Cape of Good Hope to map the southern stars and to make a series of attempts to measure solar parallax via the moon’s parallax, the opposition of Mars and a conjunction of Venus.10 Before leaving he printed a leaflet asking for the contributions of other astronomers to complete the task; among those who responded by making complementary observations were James Bradley at Greenwich and Jérôme Lalande in Berlin. La Caille’s same leaflet also contained thoughtful arguments against the transit of Venus method. He believed astronomers had developed unrealistic expectations of the degree of accuracy obtainable. In particular he stressed the ‘false security in relying upon the authority of one man in science, however great’.11 None of this dampened French interest in the coming transit of Venus. La Caille, in his criticism of the transit of Venus method stood ‘splendidly alone’.12 In 1760, Delisle completed a recalculation of Halley’s tables of planetary motions that would refine the predicted path of visibility for the coming transit of Venus. He collected these revisions into an illustrated atlas showing where and when the transit would be visible throughout the globe. Delisle’s widely distributed mappemonde became the crucial resource for the planning of expeditions throughout Europe, Britain and America. But, even before the map was published, a priority dispute over the data on which it had been based surfaced in the Académie des sciences and spread into half a dozen of the Parisian weekly journals. These quarrels brought the transit enterprise to the attention of the popular press for the

14

The Transit of Venus

first time. In a similar way, during the build up to the transit of 1874, disputes over maps would also first propel the transit into the public view.13 Financial support for the French programme was provided by a mixture of privately-funded expeditions, funding from the government (the Secretary of State and Controller-General) and from industry (the Compagnie des Indes), and transnational patronage (close cooperation with the Russian Academy at St Petersburg). Northern stations were to be in Siberian territory and in Vienna, and a southern station was planned for the French-Indian colony at Pondicherry. The location for a second southern observation site was highly contested. The south-western coast of Africa would have been ideal, but after much discussion over the numerous possibilities, such as Portuguese and Dutch trading colonies in Angola and the Gold Coast, the Académie settled on the safer (in numerous respects) option of Rodriguez, an island off the coast of Madagascar that was then in French hands. Thus, the astronomical expeditions stayed, as they almost always would, comfortably within the confines of imperial boundaries. It was only in June of 1760, when the Royal Society received Delisles’s mappemonde, that movements began towards organizing a British expedition. But this organization was swift. At a single meeting on 26 June the Council of the Society decided upon a list of desirable stations: St Helena followed by Bencoolen in Sumatra and Batavia. Bradley, the Astronomer Royal, was asked to draw up a list of the necessary instruments and their prices. On 3 July, Nevil Maskelyne, Bradley’s assistant, presented the Council with the outfit for two observers at St Helena: three 2-foot reflecting telescopes (one for the corresponding observations to be taken at the Royal Observatory), each fitted with John Dolland’s new divided object-glass micrometers (enabling observers to measure precise angular distances in the telescopic field of vision), a pendulum clock for timing the observations and a quadrant for regulating the clock. Total cost, including payment for observers and transportation, was given at £685. Although hastily organized, financial and institutional support for the enterprise was strong. It may have been stronger in relative terms than it would be in the nineteenth century. As in France, financial support would come from both the Crown and industry, in this case the East India Company. A ‘memorial’ was drawn up to justify the expense, to eventually be brought before the Treasury. The request was for £1,600. It was presented to the government via a letter to the Duke of Newcastle. As a record of how the transit programme was then couched in terms of historical pride and national honour, the letter is worth quoting at length: the Motives on which [the memorial] is founded are the Improvement of Astronomy and the Honor of this Nation; which seems to be more particularly concerned in the exact observation of this rare phaenomenon, that was never observed but once by one Englishman … [and] pointed out and illustrated by Dr. Halley another Englishman.

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And it might afford too just ground to Foreigners for reproaching this Nation in general (not inferior to any other in every branch of Learning and more especially in Astronomy); if, while the French King is sending observers … and the Court of Russia are doing the same … England should neglect to send Observers to such places … subject to the Crown of Great Britain. This is by foreign Countries in general expected from us … And the Royal Society, being desirous of satisfying the universal expectations of the World in this respect have thought it incumbent upon them … to request your effectual intercession with His Majesty … to enable them to accomplish this their desire … [which] would be attended with expense disproportionate to the narrow Circumstances of the Society. But were the Royal Society in a much more affluent State; it would surely tend more to the honour of his Majesty and the Nation in general, that an expense of this sort, designed to promote Science and to answer the general Expectation of the World, should not be born by any particular Set of Private Persons.14

The appeal here is made quite directly to national pride, specifically about the reputation of English astronomy and the desire to match – indeed outdo – any French or Russian endeavours. Particularly striking is the assertion that it is a ‘universal expectation’ that Britain will participate, as if to underline the idea that that science unfolds on an international, political stage. It is also somewhat surprising that the letter concludes with the argument that, even if the Royal Society had the funds for a transit of Venus expedition, it is nevertheless just the kind of endeavour that the government would be expected to support. Clearly the feeling was that this had to be a national enterprise. Lastly, it is important to point out here the use of history, recalling Horrox and Halley, the effect of which frames the subject as somehow a territory to which Britain has special claim. (This frame will also be used in motivating support for the nineteenthcentury programme.) On 14 July, just over a month after Delisle’s map initiated the action, the Society was told that £800 was immediately available to them, with another Royal Warrant for the remaining £800 also secured. Despite the close correspondence between French and British astronomers and scientific societies, the Seven Years War (1756–63) caused some serious disruptions to the expeditions. The two British observers bound for Bencoolen, Charles Mason and Jeramiah Dixon, had to return to England after their ship was heavily damaged by a French attack.15 And, after taking a second (much more heavily armed) ship to Bencoolen, they discovered that the island had been taken by the French. Their only option was to reverse course back to the Cape of Good Hope, where they arrived just in time to observe the transit of Venus. Similarly, Le Gentil arrived at Pondicherry to find it blockaded by the English. When the transit occurred on 9 June 1761, he was stuck on his ship, able to see the transit, but unable to make any useful observations. In addition to the six government-funded expeditions from France and Britain, many more privately-executed expeditions and individual observ-

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The Transit of Venus

ers reported results to local and national scientific societies. Woolf ’s tally puts the total number at 120 observers scattered across 62 separate stations. Many of these were well-off individuals with an interest in astronomy and access to a telescope, and who also happened to live in areas where the transit was visible. Notable are the relatively large number of German, Swedish and Italian reports; in fact there were more Swedish observers than British. Dutch, Russian, Jesuit and Portuguese astronomers also published observations.16 Debate immediately followed the publication of two different values, one from James Short in London at 8˝.56 (~154 million km / 95 million mi) and the other from Alexandre Guy Pingré in Paris at 10˝.60 (~124m km / 77m mi). These were by no means the only two calculations to be published. Woolf samples from five publications that each argued for a different result.17 In short, data from the observations did not point to a definitive value for the sun’s distance. Two problems were blamed for the disappointingly broad range of results. First, the measures of the longitudes of stations carried a significant amount of uncertainty. On some methods (Delisle’s) of calculating results this uncertainty would carry through to uncertainty in the final measure of the sun’s distance. So some of the final results would have to be recalculated after more satisfactory longitudes were obtained. The second problem was that the timing of the transit made by observers standing side-by-side disagreed by many seconds. The reasons that were given for this problem are crucial to the rest of the story and need to be explained in some detail. Recall that according to Halley’s method the observers would be trying to measure the duration of the transit with as much precision as possible. It was agreed that the transit’s duration began at the moment when the ‘lucid line of light’ appeared (when the silhouette fully entered the face of the sun, on the left-hand side) and ended with the disappearance of the lucid line of light (when the silhouette began to exit the face of the sun on the right-hand side). Delisle’s method worked on the same definition of ‘duration’ but only required observations to be taken at either the beginning or the end of the transit. But here was the problem: observers of the 1761 transit reported that the crucial lucid line, their guide to the start and/or finish of the transit, was a much more elusive phenomenon than had been expected from Halley’s descriptions. Some observers had found the moment of contact obscured by a glowing ring of light around the planet. Many more had reported that, during the conjunction of the edges of the sun and Venus, just as Venus’s edge was separating from (or coming into contact with) the edge of the sun, there was significant a distortion of the shape of Venus’s silhouette. It became elongated, as if stuck to the edge of the sun. As one observer put it: ‘The planet, instead of appearing truly circular, resembled more the form of a bergamot pear, or, as Governor Pigott then expressed it, looked like a ninepin’ (see Figure 2).18 This phenomenon, which came to be known as

The Precedent

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the ‘black drop’ or ‘ligament’, seriously complicated the task of reporting a single, precise time at which Venus fully entered and exited the face of the sun. The visual phenomena that defined the moments of contact – and, crucially, the start and/or end of the transit – were unexpectedly complex. The black drop effect was blamed for the unexpectedly poor agreement in timings among astronomers observing side-by-side. Rather than being in agreement to within a second of time, as Halley had predicted, observers had recorded times of ‘contact’ that disagreed by as much as thirty seconds. Strangely, this new complication did not dampen interest in the transit method. The efforts for 1769 were much bigger than those of 1761 had been: more time and money was spent, more observers participated, and more countries became involved. Organizational bodies and funding in France and Britain continued on the same lines of those in 1761: the Académie des sciences formed proposals and extracted support from local and colonial governments. The Council of the Royal Society formed a budget and proposal that was presented to and approved by George III. This time around, the selection of stations was more ambitious. France accepted an offer from the Spanish to set up a station at a mission at Cape Lucas on the lower California peninsula. The other two French government parties were at Pondicherry (where Le Gentil had stayed since missing the transit of 1761) and Saint-Domingue (now Haiti), then one of the richest of the French colonies. The British sent an expedition to Hudson’s Bay and to the newly discovered island of Tahiti in the Southern Seas. The latter was part of the famous first expedition of HMS Endeavour captained by James Cook and lavishly outfitted by the naturalist Joseph Banks. The astronomer was Charles Green, a former assistant at the Royal Observatory. This expedition was as much a voyage of exploration into the South Seas as an astronomical expedition, and Woolf notes that it coincided nicely with George III’s interest in geographical exploration of the southern oceans.19 In British America, Pennsylvania formed an expedition consisting of three stations along the north-eastern coast. It was funded locally by institutions such as the Pennsylvania Assembly, the American Philosophical Society and the Library Company of Philadelphia. Russia, under Catherine the Great, organized six widely scattered stations in the north, each outfitted with English instruments, including 21 telescopes by George Graham, Short and other London makers. The one other international expedition was organized by Denmark to the coast of Norway. Sweden, Germany, Holland and Spain also had observers from within their territories. All in all, 159 observations are reported. This time around the observers were better prepared for the singular difficulties of the transit observations. Instructions had been issued to help observers distinguish ‘real contact’ – when the so-called black drop appears to break – and

18

The Transit of Venus

‘apparent contact’ – when the black drop first forms. Nevertheless, the pattern of disappointment, uncertainty and debate over the results that followed the 1761 expeditions again followed those in 1769. Once again, the results were vague; a range of values for solar parallax were argued. About two hundred papers on the value of the solar parallax deducible from the 1769 transit were sent to the Académie des sciences. In sum the new results gave a probable range of 8.43 to 8.80. In 1771, Lalande put the remaining uncertainty of the sun’s distance at one million miles, clearly an improvement, but still much greater than what had been expected for the transit of Venus method.20 Those very problems would be inherited by the next generation of transit observers in 1874. But before moving on to the nineteenth century, we should consider Woolf ’s analysis of the eighteenth-century transits. His conclusion offers some useful points of departure for proceeding with this story into the nineteenth century. Woolf ’s concluding paragraph, in which he summarizes his view of the lasting impact of the transit enterprise, is abridged as follows: The cause of natural history was considerably advanced … the multiple results of this part of the transit story increased the prestige of scientific societies everywhere and lent additional weight to their future claims for a larger share of national wealth and attention. The prolonged liaison between science and government, especially with regard to the growing financial needs of science for large-scale enterprise, revealed the interdependence of science and society in very specific terms … Finally, the problem of the transits of Venus produced an intensity and breadth of effort on the part of eighteenth-century scientists that was unmatched by any other single problem. It brought to a common focus men of almost every national background with an abiding concern for the advancement of knowledge. In doing so, it helped to shape the growing international community of science and to demonstrate with striking clarity what cooperation and good will might achieve in the peaceful pursuit of science.21

First, consider Woolf ’s rendering of the transits as an example of international cooperation in science. This seems debatable, given the serious effects of the Seven Years War on the 1761 plan (that is, two of the six central expeditions were disrupted). Woolf takes as his evidence the strength and efficacy of the international correspondence among astronomers and scientific societies. However, it seems important to distinguish between international networks of astronomers and whether or not the political ideologies of the time allowed international networks of individuals to cooperate unhindered. As we will see, in the later nineteenth century, international cooperation moved from an individual level to an institutional one. At the governmental level, however, nationalistic ideologies of science, which restricted international cooperation in practice, remained as strong as ever. Second, consider how Woolf has chosen to deal with the issues of the failure and progress of the programme. Woolf clearly concludes that the story of

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the transits is not a straightforward success story: ‘Was the eighteenth-century dream of realizing the actual compass of its physical world to be achieved? Did the increased effort of 1769, numbering 151 observers from 77 stations produce a definitive solar parallax? Sadly the answer is “no” for the century of the Enlightenment.’22 Yet in his conclusion Woolf presents the story as, essentially, one of scientific progress. He does this by setting aside the simple issue of good or bad results and considering instead what the exercise as a whole involved. He focuses on the fringe benefits (to natural history, to science organizations, to internationalism in science, etc.) that went along with the enterprise. In this way, Woolf sees science as puzzle-solving in an almost Kuhnian sense (although this was written before The Structure of Scientific Revolutions), finding the markers of progress not in terms of increased knowledge or questions answered, but in how the posing of the question – the activity involved in seeking solutions – contributed to the growth of scientific activity in general.23 In a Kuhnian frame, this approach makes sense. The transits after all are episodes in ‘normal science’ through and through. Indeed, in his preface, Woolf describes the transits as the Enlightenment’s attempt to ‘complete the Newtonian system of the world’.24 Even though they did not succeed in their goal, they made an attempt on a scale larger than ever before. Does that not count for progress? Do bigger puzzle-solving efforts not also mean better puzzle-solving? As we will see, that is certainly not always the case. And if it is not always the case, we should be careful not to assume that they do go together. To gain a better understanding of progress in science, growth in science needs to be evaluated separately from progress.

2 BIG SCIENCE IN BRITAIN c. 1815–70

It is the pride and boast of every Englishman to pay his taxes cheerfully when he feels assured of their application to great and worthy objects. John Herschel (1845)1

Particle accelerators, space shuttles, the Manhattan Project – these are classic examples of ‘big science’. The term emerged after World War II as a label for the enormous scientific projects of modern times. It is sometimes hard not to see big science as a unique signature of the present day. But of course in a relative historical sense every period has had its own ‘big science’: intellectual or technological projects executed on what was a dramatic scale for the time. Historians, increasingly interested in the historical precedent for today’s big science, have begun to talk about the ‘bigger science’ of previous periods.2 The eighteenth-century transits of Venus are a stock example of early big science.3 The nineteenth-century transits are not, but only because their story is less well known. In this chapter, the outlines of what was the big science of Victorian times will be presented. The large-scale research programmes of the period share similar characteristics, such as institutional settings, programme designs, public representations and types of personnel involved. The bigger science of a period often was not the most significant or visible science in historical or even contemporary terms. For example, for the nineteenth century, Charles Darwin does not fit into this category. Neither does Michael Faraday or James Clerk Maxwell (and indeed it is largely through the lens of the history of laboratory physics that the belief that big science had no historical precedent was established). The big science of Victorian Britain has only a small place in the current historiography. And from within an account of big science in the nineteenth century, the entire landscape of scientific culture looks different. For example, from this angle the military emerges as the central institution of Victorian science. The Admiralty was especially influential on science in both cultural and financial terms. Currently however, military institutions are almost entirely absent from the historiography of Victorian science. As will be argued in ‘Admiralty Science and the Reform Movement’ below, in order to understand the political landscape as it related to government support for science, it is key to – 21 –

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The Transit of Venus

recognize the role of military science in the period. Another closely related difference that emerges relates to the issue of government science funding, which was a volatile subject of the debate from the 1830s onwards. Many historians (following the claims of Victorian actors) have argued that state funding of science was especially and even strangely weak in the nineteenth century. But, as will be discussed in ‘Admiralty Science and the Reform Movement’ below, when these large-scale Admiralty-funded projects are also taken into consideration, the picture of state science funding becomes more complex. What was big science like in nineteenth-century Britain? The transit of Venus enterprise was just one of maybe half a dozen projects that somehow stood out for their size. Many of these were concerned with vast measurement projects that involved accumulating unprecedented amounts of data. In each case the government – more specifically the military, and usually the Admiralty – would provide the manpower and material support. The following section will briefly describe one of these programmes. In the process, we will be able to connect chronologically and institutionally the transit of Venus of 1874 to its big science precedents, including the transits of 1761 and 1769.

The Magnetic Crusades: The Bigger Science Between the Two Transits In Herschel’s quote at the opening of this chapter, he was referring to government funding of the sprawling geomagnetic research programme that came to be known as the Magnetic Crusades. William Whewell called the effort ‘the largest scientific undertaking the world has ever seen’.4 Beginning in the early 1830s, Henry Sabine (and later Herschel, William Whewell and others associated with the British Association for the Advancement of Science; BAAS) began to press for a major new expeditionary study of magnetic variation. The ‘geomagnetic lobby’, as John Cawood calls the group, organized from within the BAAS a proposal to establish a global system of magnetic measurement. Sabine was an officer of the Royal Artillery and in the 1820s had been in charge of scientific investigations for Arctic expeditions. He was based at Woolwich Arsenal, under the wing of John Barrow, Secretary of the Navy from 1804 to 1845, and perhaps the most powerful figure in Admiralty science at the time. Throughout his career, Sabine would benefit directly from these connections. In 1828, for example, he was appointed the Royal Society’s Scientific Advisor to the Admiralty. There were two parts to the proposed plan of the BAAS: a voyage to the South Polar regions to map magnetic variation around the Antarctic, and a network of small magnetic observatories stationed at colonial outposts throughout the world that would map the temporal changes in magnetic variation. Sabine’s goal was to derive simple laws of magnetic variation from a large set of worldwide

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23

observations. He expected this data to provide some means of settling the ongoing debates about the origin and nature of magnetism. Momentum behind the project also came from a number of other directions. Most obviously, there were urgent practical reasons to investigate geomagnetic variation: new iron ships disrupted compass readings, and inaccurate bearings had been directly linked to lost ships and lost lives. In Cawood’s thorough study of Sabine’s enterprise, however, the most stress is placed upon the ideological importance of the proposal: ‘It must be recorded that as far as the Admiralty was concerned the primary objectives of the voyages were political, economic, or prestigious’.5 (Note as an aside that, exactly as with the transits of Venus in the eighteenth century, the justification of government funding took the form of ‘a plea to the British to vindicate the ideas of their fellow countryman Halley’; here is another example of national historic pride with respect to the history of science playing a role in justifying particular research programmes.6) Cawood also argues that British interest in geomagnetic expeditions in the 1830s and 40s was motivated to a large degree by concerns over the relative status of French and British science. In geomagnetism, France was then considered to be clearly in advance of Britain. Recent work by Alexander von Humboldt, Jean-Baptiste Biot and François Arago had put the Paris Observatory at the forefront of magnetic research. Sabine’s massive datagathering scheme was sure to challenge that hegemony. Crucial to the take-off of the plan was the support of John Herschel, who had even deeper connections to the government than did Sabine. Herschel pressed for the magnetic expeditions directly to the Prime Minister, Lord Melbourne, the Chancellor of the Exchequer, and the Queen.7 The proposal eventually put to the Government included a request for £400 for the Antarctic expedition, and, for the colonial observatories, £2,000 per observatory. The Antarctic geomagnetic expedition, which set out in September 1839, was especially marked by international rivalry, as the Americans (1838–42) and the French (1837–40) lauched their own Antarctic expeditions. Germany, Russia and Norway also had expeditions around this time. These Arctic and Antarctic voyages of exploration would dwarf, in financial terms, any of the astronomical or geomagnetical programmes supported by the Admiralty in the nineteenth century, including the transits of Venus. For example the British geomagnetic Antarctic expedition would, by 1843, reach a cost of £109,768.8 The establishment of the system of British colonial observatories was not nearly as swift as the organization of the Antarctic expeditions. Cawood suggests that the navy felt satisfied that issues of national prestige were being sufficiently served by the Antarctic expedition, and that the colonial observatories did not have the same political pay-off. By early 1840 it was agreed that the cost would be split across the Admiralty, the War Office and the East India Company jointly, together with various other forms of cooperation with other governments and

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The Transit of Venus

individual support. Altogether there were thirty-three stations. The Admiralty and the Royal Artillery supported stations at Greenwich, Dublin, Toronto, St Helena, the Cape of Good Hope and Van Diemen’s Land (Tasmania). The East India Company supported stations at Madras, Simla, Singapore and Bombay. The Russian government supported ten stations in European and Asiatic Russia plus one at Peking. Cooperating observatories included Milan, Prague, university observatories at Philadelphia and Cambridge (Massachusetts), Algiers, Breslau, Munich, Cadiz, Brussels, Cairo (supported by the Pacha of Egypt), Trivandrum (supported by the Rajah of Trivandrum) and Lucknow (supported by the King of Oude). These observatories were to take synchronized observations of the ‘magnetic elements’ on certain days of each month. According to the first report of the committee, by 1840 most stations were taking measures on a two-hourly basis, and on each term day per month at two-minute intervals. Despite internal disputes over the locations of more observatories, especially a proposed physical observatory in London separate from the Royal Greenwich Observatory, the far-flung programme remained cohesive, and the government’s support was successfully obtained for a further six years. The results of the Magnetic Crusades in no way met the hyperbolic claims laid out by the geomagnetic lobby in the 1830s. Mountains of data were collected, but, as would be typical of these large research programmes in the nineteenth century, most of the data went unanalysed or even unpublished.9 Cawood concludes that the political aspects of the crusade were probably more important than ‘its immediate scientific consequences in early Victorian science’.10 In briefly comparing Woolf ’s study of the eighteenth-century transit of Venus expeditions to Cawood’s study of the Magnetic Crusades, a few interesting points emerge. Cawood is much less inclined than Woolf to ascribe any internationalism in science to the enterprise, even though in his case there was some direct cooperation between governments, notably between Germany and Britain. Its political value brought support from the government and the Admiralty, but, in what Cawood sees as a period of worsening international relations and rising nationalism, ‘national factors sometimes predominated in a science which only two decades earlier had been based on the international cooperation of private individuals’.11 Like Woolf, however, Cawood also finds a story of progress in terms of the Magnetic Crusades’ effect on the growth of scientific activity. The absence of the result that was desired is not given as much weight as the very fact of the exercise, which in itself is seen as progress. For example, according to Cawood the most important outcome was the foundation of the system of colonial observatories. For decades these continued to feed data to Sabine and his staff at Woolwich, although it is unclear what was done with that data. Thus in his analysis of the outcome of the Magnetic Crusades, Cawood makes the same conclusion that Woolf did in The Transits of Venus: growth in science is read as progress in sci-

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ence, and in this way cases of failures in the history of science – failures to obtain results, meet stated objectives or achieve the desired growth of knowledge – are paved over by the story of the growth of scientific activity. That it was big science is thus rendered as progress in itself.

Admiralty Science and the Reform Movement The same ideologies of national scientific prestige that gave some push to the Magnetic Crusades also were at the root of a prolonged push for the reform of science funding and education that began in the late 1820s. The foundation of the BAAS in 1831 was one early outcome of that push. Reformists such as Charles Babbage and Sir David Brewster sought increased government involvement in the promotion of science, and argued that the wealth and stability of the country depended upon national institutions for scientific education and research. The expressions of concern often took the shape of comparisons between the systems of national science education and research in France and Germany and the relative lack of such organization in Britain.12 As Cardwell puts it, ‘the Decline of Science movement … was actuated by the recognition that Continental nations had begun to organise science for the national good: that it was taught in their schools and universities, that it was beginning to permeate their workshops and factories, and that the advice of men of science was sought and heeded by their governments’.13 It was widely recognized that science in Britain was more dependent upon wealthy individuals than it was in other countries. There was a persistent concern over the central role played by wealthy amateurs in British scientific culture. By the 1860s and 70s, the push for reform had gained critical momentum. Public institutions for science, such as the South Kensington Museum, were beginning to emerge. Government committees were appointed to consider the issue. Oxford and Cambridge would soon get their first science departments. Yet for many change was still much too slow. As the twentieth century approached, that concern would only intensify. As late as 1898 it would be argued by William Thomson, Lord Kelvin, that ‘the best of experimental physics in this country has been undertaken by wealthy amateurs’.14 These critics were moving against a more entrenched view that supported the traditional individualist culture of British science. Proponents of the traditional view generally distrusted the state’s ability to promote and manage science, and believed that its liberal, self-governing attitude towards science should not be allowed to continue. The state, they claimed, was not capable of making informed decisions about the allocation of funding for science, and its intervention was most likely only to benefit the personal interests of those in the government.15 George Airy and Richard Anthony Proctor are examples of those who were in

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The Transit of Venus

opposition to the reform movement. As Proctor put it in 1876: ‘the demands of science should be moderate until experience has shown the advantage of acceding to them. Our Government has to be educated in these matters, and it would be as unwise to begin with large and complicated schemes as to try to educate a schoolboy by making him read Newton’s Principia’.16 Strangely, neither side of this debate included in their image of state science (whether positive or negative) the role of the government’s largest funding body for science: the military.17 The military – especially the Admiralty – was by far the most important patron of science in the nineteenth century. Between the Napoleonic Wars and the Boer War, the navy was especially active in conducting scientific expeditions and in promoting a culture of observation and data collection among its officers.18 Throughout the nineteenth century, the army and the navy regularly included in their annual supply estimates over £100,000 each for works designated ‘scientific’.19 Even for individual enterprise, the Admiralty provided most grants and prizes, such as the longitude prize and the series of grants totalling £17,000 that Babbage received for his calculating engines in the 1830s. Smaller-scale funding was also common, especially for astronomy. For example, in 1857 the Astronomer Royal arranged for the Admiralty to pay the French astronomer P. A. Hansen a £1,000 prize for his work on the lunar tables, and in 1860 Airy obtained £500 for the solar photographer Warren De La Rue’s eclipse expedition. The Admiralty also trained and represented the greatest number of science workers in the country. For example, when London’s private technical schools were rated by the Committee on Education in 1868, the Royal Engineers provided the assessors. The Royal Naval College claimed to provide the most thorough training in sciences available. In 1873 there were even accusations in parliament that the ‘hard scientific system’ at the College was too demanding, thus ‘emasculating those higher and manly qualities which had hitherto characterised our naval officers, and upon which our naval renown was founded’. But most MPs seemed to agree with the Admiralty’s reply that ‘the Navy should continue to have, what it had always possessed, officers skilled in the highest branches of science. There was no other profession which possessed in its ranks men of higher scientific attainments.’20 Before national laboratories and university-based science programmes created career paths for science workers, the military was the place to find them. The Admiralty’s culture of science was fostered, promoted and codified in the Admiralty Manual of Scientific Inquiry, edited by John Herschel and first published in 1849. The Manual is structured as a long list of subjects and subdivisions of subjects that, for the ‘honour and advantage of the Navy … and the general interests of science’ it considers worthy of attention. A partial list includes astronomy, botany, geography and hydrography, geology, mineralogy,

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magnetism, meteorology, statistics, tides, zoology and ‘independently of matters of exact science … reports upon national character and customs, religious ceremonies, agriculture and mechanical arts, language, navigation, medicine, tokens of value, and other subjects’.21 Servicemen were encouraged to develop scientific hobbies, which, the Manual suggested, could lead to monetary rewards. Even among the civil service secretaries in London, a culture of science was evident. In the later half of the century, the War Office was notoriously overstaffed and its undemanding work environment nurtured a number of the period’s scientific (and literary) figures, such as the astrophysicist Norman Lockyer.22 Yet the ‘scientific servicemen’ of organizations such as the Royal Engineers, the Royal Artillery and the Royal Marine Artillery have only a shadowy presence in the current historiography of Victorian scientific culture.23 Indeed, given the absence of military funding in the debate over science funding throughout the nineteenth century, it is unclear how this sector of science workers was viewed at the time. For the most part, the ‘Decline of Science’ camp seems to have been critical of military-science culture. The subject of the Admiralty appears in a few nuances in some of the reformers’ positions, in particular those of Charles Babbage in Reflections on the Decline of Science in England (1830). The relationship between the Admiralty and astronomy had been a long-standing issue for Babbage. In Reflections that relationship is singled out for criticism. Babbage argued that honours and funding should go more to those practising the mathematical sciences and less to those involved in descriptive science (such as at colonial observatories) or merely taking a general and amateurish interest in the sciences.24 The type of amateur Babbage targeted was, specifically, the military or civil service officer. It should thus come as no surprise that Babbage was no fan of Sabine or the Magnetic Crusades. Indeed Babbage also singled out Sabine for attack in the Reflections, where he was accused of falsifying observations, of not deserving his post and of being subservient to the Admiralty.25 Sabine in fact exemplifies another thriving form of Victorian scientific amateurism, one that was not restricted to the wealthy; he was a science worker by way of by practical military training. As Babbage saw it, this class did not have the means or training, or perhaps ability, to make any contributions to science beyond accumulating data. The historiography of government science in Victorian Britain can appear to divide along civil-military lines. On the civil side, historians such as Cardwell, Poole and Andrews, who have studied the reform movement and government policy on public science – not militarily-connected science – in Victorian Britain, have shown a clear lack of government support for it until about 1900.26 Ranging well beyond the reform movement, Roy MacLeod has traced through nearly a dozen case studies in the piecemeal revolution of civil scientific expertise, whereby the ‘inspector-generals’ of the eighteenth century were replaced

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The Transit of Venus

by ‘scientist-inspectors’ of the nineteenth century. Following the meritocratic reforms of the civil service in the 1850s, agencies such as the Board of Trade, the Board of Education and the Treasury were gradually infiltrated by a new class of civil servants who brought particular scientific skills to the job. On this view, the multiplication of the ‘man of science’, a ‘statesman in disguise’, throughout the civil branches was part and parcel of the explosion in Britain’s civil bureaucracy in this period.27 On the military side, historians working on the relationship between science and empire – almost always militarily-connected science – have emphasized the strength of government interest in science throughout the nineteenth century. They have argued that the Victorian state was acutely aware of the value of scientific research to the Empire. According to Ashworth, rather than neglecting to engage with science, the state actually tried to mimic or appropriate the observation and reporting techniques common to Victorian science. The Admiralty Manual of Scientific Enquiry is the literary embodiment of what Ashworth has called the ‘roaming eye’ of the British Empire.28 As Ashworth has written about the importance of ‘networks of information’, Headrick has written about the importance of networks of technology, to the acquisition, management and exploitation of territories.29 Sabine and the Magnetic Crusades fit this pattern of geographically dispersed and voluminous measurement schemes. The Magnetic Crusades were especially suited to benefit from the ‘amateur scientists’ in the ranks of the army and navy. Britons overseas, officers and non-officers alike, who had an interest in geomagnetism were invited to make measurements, and official forms were provided for them to complete. This was not always the case; in interesting contrast, and in support of the idea that in Britain there was a uniquely strong military culture of individual or amateur scientific participation, in the French research programmes, Biot and Arago were reluctant even to allow data to be collected by naval personnel.30 Babbage’s calculating engines also fit this pattern; they were designed as a solution to the bottleneck (and perceived high frequency of human error) in processing the industrial quantities of numerical data being collected throughout the Empire. All of this was big science as ‘horizontal integration’.31 It was a good fit for – and arguably a direct product of – the widely distributed colonial context that dominated Victorian government science. That context would also be crucial to the transit of Venus expeditions in 1874 and 1882. In fact, the more public, civiloriented realm of the BAAS (the Magnetic Crusades was an exception) would have nothing to do with the transit enterprise; for example, in John Tyndall’s famous presidential address to the annual BAAS meeting in Belfast in 1874 (traditionally an occasion for the president to discuss the major scientific events of the year), no mention of the transit of Venus was made at all.32 The disjunction in the historiography between the world of military state science and civil state sci-

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ence rightly reflects the space between those two spheres at the time. The upshot is that, although the transit enterprise emerged just at a time when the status of state science was under the microscope in the press and in parliament, this research programme would not become an instrument – or indeed even become a presence – in that wider debate.

Airy’s Greenwich and its Place in the Historiography Many historians have suggested that if anything was at the centre of the Victorian network of military-imperial science it was the Royal Greenwich Observatory. While Babbage and the BAAS may have stood at the threshold of government science with one foot in the door, the man already inside, and keeping a close eye on the jostling in the doorway, was the Astronomer Royal George Biddell Airy. Airy may not have been the first public science servant in Britain, as some historians claim, but he certainly was in his time among the most prominent.33 He was also, as mentioned above, somewhat hypocritically against the reform movement’s push to expand government funding for science. Airy was thus frequently critical of new proposals; he was the only major figure who stated objections to the Magnetic Crusades, he was against Sabine’s proposal for a magnetic observatory at Kew, and he was equally opposed to later proposals by other reformers (Balfour Stewart, Benjamin Lowey and Norman Lockyer) for an astrophysical laboratory at Kew.34 About six miles from central London, perched on a hill above Blackheath and surrounded by manicured parkland, the turrets and domes of the Old Royal Observatory (built 1670) formed the familiar architectural skyline of Greenwich. Now a World Heritage Site, Greenwich was even more of a landmark institution in Airy’s time; it was the active and visible centre of British science. Airy was Astronomer Royal from 1835 to 1881, and his effect on the institution was enormous. Throughout his long career, Airy retained and reinforced Greenwich’s devotion to positional astronomy. This involved mapping the sky by observing the transits of stars and other celestial objects across the Greenwich meridian. The core instrument was Airy’s famous transit circle, installed in 1851, which he designed and had constructed by the engineering firm (with connections to the Airy family) Ransome and May. It would remain in use at Greenwich until 1954. His method for reducing the transit circle observations of the time and position of stars, planets and the moon as they crossed the meridian – codified in printed worksheets filled out by the observatory computers – also became a legacy. It remained virtually unchanged until the 1940s.35 Because of its connection to navigation, positional astronomy has a long history of government patronage. But by the 1850s the use of positional astronomy to navigation had all but expired. Government observatories had outgrown their

30

The Transit of Venus

practical origins. The longitudes of almost all major ports in the world had been determined to a precision required for navigation, and marine chronometers were finally cheap and reliable enough to have almost entirely replaced any other methods relying on astronomical observation.36 Meanwhile, Greenwich’s most fundamental work of charting the stars, the moon and the planets had reached a level of accuracy that surpassed the needs of navigators. That work had, by this time, become an end in itself. Beyond producing ever-better predictions of celestial motions – the same kind of data-focused project as those of Sabine and Babbage – the other products of precision astronomy were related to natural constants of interest to physical theory, such as measures of the gravitational constant or the speed of light. Greenwich had thus completed its mission with respect to navigation. This is not to say that Greenwich did not perform useful functions for the Admiralty and for the government in general. Although the primary, central function of the observatory continued to be positional astronomy, Greenwich also had a new routine of utility: distributing time and taking meteorological and magnetic observations. From mid-century, accurate mean solar time was recorded at Greenwich and distributed via telegraph throughout the country. This was its primary civil function.37 On-board ship, Greenwich time was kept by chronometers, usually about a dozen per ship, each of which – as will be described later on – required a battery of rating and testing pre- and postvoyage. At Airy’s insistence a whole separate observatory at Liverpool had been built just to handle the navy’s chronometric load. At the same time, however, through sheer power of tradition, government patronage of positional astronomy continued to grow throughout the nineteenth century.38 This is, in general, one of the most puzzling aspects of nineteenth-century astronomy, and one which remains largely unexplained. Some historians have thus concluded that the purpose of late-Victorian positional astronomy was essentially symbolic. As Bennett put it: Such was the enthusiasm for precision astronomy, and the prestige attached to it, that the fashion for founding observatories was greater than ever. The functions of official observatories in particular were to a large degree symbolic … There was generally no clear theoretical aim to the exercise and the observations themselves often remained unpublished, or if published remained unused.39

But the question remains as to why such symbolic importance might carry such weight at the time. What is clear is that, by the 1850s, Greenwich owed its pride of place in culture and politics mostly to historical precedent. At the time of the transits of Venus, positional astronomy continued to hold a very privileged position as the only branch of pure science (as it was then called) with regular and substantial

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government support. Despite a naval budget squeeze in the early 1870s, the transit enterprise would meet no resistance as it grew in size and scale. Historians have covered Greenwich during Airy’s tenure from many different angles, which can be classified into three general approaches: 1. Victorian Greenwich as prototype or early example of an institution of ‘public science’;40 2. Victorian Greenwich as a central product of and contributor to the needs and interests of the Empire;41 and 3. Greenwich as the iconic newly emergent industrial science, as an observatory-factory and an institution of cultural domination.42 Each approach deals in different ways with Greenwich’s (and Airy’s) evident high profile in Victorian scientific culture. All draw out important aspects of the contemporary conception of Greenwich or of its lasting significance. The third category, especially Simon Schaffer’s 1988 article on Victorian Greenwich, is by far the most influential in the recent historiography of the institution. Schaffer gives an implicitly Foucauldian analysis of Airy’s management of the observatory: ‘The observatory became a factory, if not a panopticon’.43 The article draws on the ways in which Airy reformed the working routines of the observatory, most importantly new efforts to introduce a standardization of observations. The parallel between between the factory system and Airy’s management of the observatory was also drawn in Airy’s own time. Simon Newcomb, director of the American transit of Venus expeditions in 1874, wrote that Airy’s legacy as ‘the most commanding figure in the astronomy of our time’ owes as much to his astronomy as ‘his ability as an organizer’: … he introduced the same sort of improvement that our times have witnessed in great manufacturing establishments, where labour is so organized that unskilled men bring about results that formerly demanded a high grade of technical ability. He introduced production on a large scale into astronomy.44

Greenwich was known for the high quality and high output of its publications. In addition to the factory comparison, this reputation for efficiency also invited parallels to large accounting offices, themselves symbols of modernity in the nineteenth century.45 But it is the Foucauldian approach that has spread far and wide, now appearing as an assumption in not just Greenwich historiography but also, increasingly, in other areas of Victorian science studies. On this view, scientific ‘elites’ such as Airy and John Herschel are depicted as policing or disciplining the senses of the amateur class (especially via the personal equation discussed in the Introduction), as a means not only of conducting research programmes but also of controlling social unrest in society at large.46 Such claims go well beyond what Ashworth and Smith argue for in their evaluations of the role of amateur networks, but even their insights carry an assumption that there was something

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The Transit of Venus

akin to a repressive social class hierarchy at work within the large network-based research programmes of the Victorian era. There are a few arguments against the more extreme view. First, beyond Greenwich, just who the amateurs are in Airy’s or Herschel’s networks of information-gathering (for example in colonial observatories) is rarely addressed, but the answer to that question is key. The vast majority were members of the military or the civil service. I would therefore argue that any ‘discipline’ received by way of instructions for astronomical observations must be inconsequential in the face of the adherence to discipline inherent in their identities as officers. In other words, if indeed there was any new disciplinary regime under which networks of observers then operated, it was a regime imposed by the military, not by Airy or Herschel. Giving these figures too much influence may in fact obscure the real power dynamic in Victorian science, which rested with the military and its social structures. Second, within Greenwich, the evidence used to support the notion that Airy reformed the labour structure in the Observatory according to ideals of industrialization comes from the fact that Airy saw the labour of observation as manual, and that he referred to his observers as ‘drudges’. But that attitude had been in existence at Greenwich well before Airy’s time. Until 1765 the Admiralty’s job description for observatory assistants was ‘servant or labourer’ and only changed to ‘assistant’ after Nevil Maskelyne (Astronomer Royal, 1765–1811) lobbied for its change.47 Maskelyne advertised for men who were ‘to be sober & diligent & be able to bear confinement’. At that time assistants slept and lived in a room attached to the observing room, and were allowed very little individual freedom.48 Maskelyne’s successor John Pond (Astronomer Royal, 1811–35) wanted his assistants to be ‘indefatigable hard working & above all obedient drudges … men who will be contented to pass their day in using their hands & eye in the mechanical act of observing & the remainder of it in the dull process of calculation’.49 And that labour hierarchy would continue long after Airy was gone. As one former Greenwich employee recently recalled: ‘It was made quite clear to recruits in the 1930s who had bright ideas about possible improvements that they were not paid to think, they were paid to do as they were told’.50 In Airy’s time, entry-level observers did occasionally rise through the ranks of the Observatory; others went on to jobs in accounting or the government. Chapman in particular provides convincing evidence that the working conditions in the Observatory were relatively good, especially compared to those endured by labourers in real factories.51 Airy and his predecessors and successors did not seek to install a means of surveillance and control within the observatory as an end in itself. The social structures and the disciplined nature of observatory work were unintended – albeit fascinating –consequences of the dogged pursuit of increased precision

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(hence the training of observers, the mechanization of observation, the division of tasks) within a military patronage system (hence the ‘production on a large scale’). This is the situation around which, for hundreds of years, everything at the Observatory would be organized. What is fascinating is how, by Airy’s time, precision had become an end in itself. Nothing brings that out so clearly as the transit of Venus enterprise. The pursuit of precision in the transit of Venus enterprise would lead Greenwich hastily to graft experimental measurement techniques onto its refined practice of positional astronomy. And in this situation, Airy’s ‘disciplinary regime’, if there is one at all, was more his ideal fantasy than the reality of the working life at the observatory. Airy does not come out as a mastermind of discipline and surveillance. He delegated important parts of the programme design to hired staff and even to volunteer amateurs. If anything, he struggled to maintain control and he did so – at times – by insisting on petty procedural dictums. Furthermore, the training of observers’ senses did not amount to a loss of the status or authority of those individuals. Certainly in the transit enterprise, as we will see, success was seen to depend absolutely on a principle of environmental, procedural and instrumental uniformity. That principle would be pursued intensely but with only limited success. And, as will become clear, the motivation behind that principle rested in the problems raised by large-scale precision measurement, by the instruments then in use, and by how those problems were approached in nineteenth-century astronomy. If we now consider the question of where the transit enterprise should be situated with respect to Victorian science in general, it should be clear that the answer must be given on a few different levels. First is its status as a ‘pure science’ astronomical pursuit, together with the symbolic value conferred on positional astronomy generally, and to Greenwich in particular, by the route of tradition. Second, as an element of military science, it is in company with and shares many characteristics of other big science ventures of the time. At a time when Britain was responsible for roughly half of the world’s maritime commerce, it should come as no surprise that the big science of the nineteenth century was Admiralty science. Most involved recording huge amounts of precision measurements, projects that (either directly or indirectly) involved gaining further knowledge and control of the sprawling resources of the British Empire. That was a speciality of Greenwich. Examples include not only the Magnetic Crusades, but also the pioneering oceanographic survey of HMS Challenger (1872–6), the Geological Survey of Great Britain (begun in 1835), the Great Trigonometrical Survey of India (begun in 1814), as well as the trigonometrical surveys of Great Britain and Ireland begun in the first half of the nineteenth century.52 This is the institutional and political context to which the transit of Venus enterprise belongs. As we will see in the next chapter, a distinct though not

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necessarily unique sentimentality about science drove interest in the transit enterprise. Some of this would draw on the special status afforded to astronomy at the time. In Airy’s words, it was a pursuit of the answer to ‘the noblest problem in nature’. In the words of the New York Times, it was ‘the astronomical event of the century’.53 But, as we will see, the establishment of the enterprise would be driven most of all by the ‘great exhibition’ context of international competition.

3 NOBLE SCIENCE, NOBLE NATION: THE ESTABLISHMENT OF TRANSIT PROGRAMMES IN BRITAIN AND ABROAD

But the facts are now patent; the scientific honour of our country is at stake. The Times (London), 8 February 1873

By the late 1850s, the Royal Observatory was running at the high level of efficiency for which, as was described in the previous chapter, Airy’s tenure was already well known. After two decades as Astronomer Royal, Airy was a central and powerful figure in British science. He had not entirely avoided controversy. The recent loss of priority of the discovery of Neptune to the French was a huge blow to his public image.1 Airy’s work on ship magnetism had brought him some notoriety as well; a ship was controversially lost just after its compasses had been adjusted according to Airy’s method.2 It was from the operation of Greenwich meridian astronomy, however, that Airy maintained his upstanding character. There was a regular time service and a regular output of astronomical observations. Subjects on which the observatory steadily published included observations of minor planets, tables of the moon’s motion, longitude determinations of foreign observatories, and refinements to the instruments of precision astronomy.3 Against this backdrop of routine observation, Airy introduced plans for attacking the problem of the sun’s distance. The value of the sun’s distance (then referred to in terms of solar parallax), was continuously refined throughout the nineteenth century.4 During the 105year gap between the eighteenth- and nineteenth-century transits of Venus, astronomers recalculated and reanalysed the 1761 and 1769 observations, sometimes when improved values of longitude for the observation stations were made available, sometimes when new approaches to the selection and combination of observations were developed.5 As the Edinburgh Review put it in 1873, ‘many restless astronomical spirits … continued to nibble at these figures’.6 In 1825, Johann Franz Encke produced a parallax of 8˝.54 (~154m km / 95.7m mi) by updating the longitude data for the results from the 1761 and 1769 transits. The British Nautical Almanac used this value from 1834 to 1869. By – 35 –

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mid-century this value was being challenged by new determinations such as that of Peter Hansen in 1857, whose calculations of the sun’s gravitational effect on the moon resulted in a parallax of 8˝.97 (~146.6m km / 91.1m mi). From 1870 to 1881, the Nautical Almanac would use 8˝.95 (~146.9m km / 91.3m mi), a value derived primarily from Hansen’s work. A third method depended upon precision measurements of the speed of light, which in conjunction with annual observations of the eclipse of a moon of Jupiter give a measure of the sun’s distance. Leon Foucault’s measure of the speed of light using rotating mirrors was first attempted in 1848 and would later be refined in the 1870s and 1880s by Albert Michelson.7 Yet, as we will see, the transit of Venus method would retain a certain appeal until the end of the 1870s. In 1857 Airy gave a lecture at the Royal Astronomical Society entitled ‘On the Means which will be Available for Correcting the Measure of the Sun’s Distance, in the next Twenty Five Years’. He described the scientific and symbolic importance of the measure in the following way: The measure of the Sun’s distance has always been considered the noblest problem in astronomy. One reason for this estimation is, that it must be commenced as a new step in measures … A second reason is that, in whatever way we attack the problem, it will require all our care and all our ingenuity, as well as the application of almost all our knowledge of the antecedent facts of astronomy, to give the smallest chance of an accurate result … A third reason is, that upon this measure depends every measure in astronomy beyond the Moon; the distance and dimensions of the Sun and every planet and satellite, and the distances of those stars whose parallaxes are approximately known8

There were a number of possible approaches to the problem, and at first Airy was hesitant about the transit of Venus method. He gave serious consideration to the method based on observations of Mars in opposition.9 In 1860 he published maps and instructions for making such observations, and his chief assistant at the Royal Observatory made an attempt in 1862. Later on, in 1872, at the height of transit preparations, he would confess to Norman Pogson at the Calcutta Observatory, ‘I really am disposed to think that the Mars observations, through a long series of years, will give results at least as trustworthy as the Transit of Venus’.10 In his initial ambivalence towards the transit of Venus method, Airy was not alone. The director of the Paris Observatory, Urbain Le Verrier, also thought other cheaper methods would give equally good results. But, while Le Verrier would maintain his distance from the French programme, Airy ended up at the head of the massive British endeavour. It is clear Airy felt a sense of duty towards the transit of Venus, perhaps believing that the weight of tradition (and ‘the future astronomical public’ he addressed in his final remarks) required a Greenwich transit of Venus programme.

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Figure 2. The black drop as drawn by observers in 1769. From R. Proctor, Transits of Venus, from the First Observed A.D. 1639 to the Transit of A.D. 2012 (London: Longmans, Green, 1874).

Edward Stone, the Black Drop Effect and the Transit of Mercury in 1868 Recall that Halley’s original idea to measure the distance to the sun using a transit of Venus came to him, as he said, when he observed the ‘lucid line’ demarcating the start and end of a transit of Mercury at St Helena in 1677, and that, as astronomers discovered when the next transits arrived in 1761 and 1769, the crucial lucid line was a much more elusive phenomenon than Halley had suggested. Instead, what most of the observers reported during the contact of the edges of the sun and Venus was a distortion of Venus’s silhouette just as its edge was breaking away from (or coming into contact with) the edge of the sun (see Figure 2 above). Agnes Clerke gives a memorable description of the black drop effect: ‘It may be described as substituting adhesion for contact; the limbs of the sun and planet, instead of meeting and parting with the desirable clean definiteness, clinging together as if made of some glutinous material, and prolonging their connection by means of a dark band or dark threads stretched between them’.11 The so-called black drop phenomenon quickly became the focus of the attention of nineteenth-century astronomers. In Britain, no one spent more time evaluating the black drop issue than Edward James Stone.

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Stone had been a chief assistant at the Royal Observatory, Greenwich, since 1860. Throughout his career, he worked on the measure of the sun’s distance. He had observed the opposition of Mars in 1862, and from that had calculated a value of 8˝.94 (~147.1m km / 91.4m mi) for solar parallax.12 He then went on to a detailed re-evaluation of the transit of Venus observations from 1761/9. According to Stone, a re-evaluation was called for by the growing disagreement between the most accepted 1769 transit value of 8˝.54 (~154m km / 95.7m mi; by Encke in 1824), and the recent results of lunar theory, speed of light measures and Mars in opposition, all of which pointed to a parallax of at least 8˝.9. This growing disparity did not diminish Stone’s confidence in the soundness of the transit of Venus method – he saw ‘great skill and judgement’ in the execution of the transit programmes in 1761/9 – only in the way the data had been analysed. In his new study of the eighteenth-century data, Stone was looking for sources of ‘systematic error’ or of ‘wrong interpretation’ which ‘might be feared and ought to be guarded against’ in the observations proposed to be made in the transits of 1874/82.13 In June of 1868, he published an analysis of the 1769 reports. What Stone found in his analysis were errors of ‘interpretation’. Each observation of contact typically consisted of numerous times, such as Father Sajnovics’s recording of ‘contactus dubius certus’ at 15 hours, 26 minutes, 18seconds and ‘contactus certus’ at 15 hours, 26 minutes, 26 seconds.14 The difficulty with the transit observations – the difficulty caused by the complexity of contact – had always been this: which of these times shall be taken as ‘contact’? The ‘contactus dubius certus’ might have been too early, and the ‘contactus certus’ might have been too late. Should some time in between be taken, should one of the two times be selected, or should the observation be rejected altogether? Stone’s theory was that the black drop effect actually appeared at ‘true’ contact, and that at what looked like ‘geometric contact’ (when the edges of the sun and Venus appear to intersect, what he also called ‘apparent contact’) was actually after the edge of the planet’s silhouette had passed the edge of the sun. It is less important that Stone was arguing that the black drop occurred at ‘true’ contact (and later Stone’s theory would be reversed). More importantly, the black drop was no longer being considered a disturbance or side-effect obscuring contact. It was now being treated as a legitimate phase of the observations. Stone’s new approach legitimated those ‘dubius certus’ times, since they were now interpreted not as uncertain observations but as valid observations of a distinct phenomenon. Stone selected observations in which it was clear that the observer had recorded either ‘geometric contact’ or ‘true contact’, as in the formation of the drop. He found that the difference between observations at the same station of geometric contact versus the formation of the drop was about sixteen seconds, and he thus calibrated the observations accordingly, so that all

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observations, in effect, referred to the formation of the drop. In short, Stone used the black as a new ‘lucid line’: the effect by which the timings of the contact observations were aligned. On this basis, he succeeded in producing a new value of 8˝.91 (~147.6m km / 91.7m mi) from the eighteenth-century reports. I consider therefore that by simply interpreting strictly the language employed by the observers, I have been led to a solution which satisfies the whole of the ten observed durations, and gives at the same time … a satisfactory result for the difference between the time of internal contact and the breaking of the black drop.15

(Note the focus on how to interpret the observation language; that issue will be central to the rest of the story and will become especially important in Chapter 4.) The results themselves did not have a wide impact on the contemporary value of solar parallax, but because Stone’s approach produced a more agreeable value of parallax from the transit data, his approach to the black drop problem was influential. The gold medal of the Royal Astronomical Society was awarded to him in 1869 for this work. Despite Stone’s apparent success in reinterpreting the results, there was a deeper problem with the transit data that Stone’s work had not relieved. The form of the data – multiple numerical timings anchored to descriptions of what the timing referred to – left plenty of room for disagreement over how the observer reports should be interpreted. Simon Newcomb’s criticisms of Stone’s 1868 paper illustrated the problem clearly. Newcomb was Professor of Mathematics at the United States Naval Observatory and he would be a leading member of the United States Commission on the transit of Venus, the managing body appointed by Congress. It was a simple but important disagreement: Newcomb was not convinced by Stone’s interpretation of the 1769 observer Chappe’s observation of egress. Stone understood Chappe to have referred to the formation of the black drop when signalling contact, while Newcomb thought Chappe’s words clearly referred to geometrical contact. The difference was not insignificant. According to this interpretation, Chappe’s recorded duration of the transit was a few seconds longer, and Newcomb’s result for solar parallax was correspondingly smaller at 8˝.86 (~148.4m km / 92.2m mi) rather than Stone’s 8˝.91.16 This debate perfectly highlights the sensitivity of the result to the way the observation language was interpreted. A different – and entirely reasonable – interpretation of a single observation produced a difference of half a million miles. So, even as the black drop effect gained new status as a useful aspect of the observations, the descriptive language of observation reporting still left the data open to multiple interpretations. Attempts to restrict or regulate the way that observers both saw and reported the contacts would thus become a priority during preparations at Greenwich.

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As in the eighteenth century, the transits of Mercury that preceded the transit of Venus were widely observed in the hope that something useful would be learned about the coming transit of Venus. During the Mercury transits of 1861 and 1868, it became almost a sport among interested astronomers to hunt for evidence of the black drop effect. William Lassell had been in Malta for the transit of Mercury in 1861 and watched carefully during contact: … the image was, with occasional slight disturbances, as sharp as can be conceived … I scrutinised the planet well throughout its transit, but could not be sure of any peculiarity. I repeatedly fancied it a little elliptical, but I do not believe in the reality of the appearance.17

John Hartnup at the Liverpool Observatory described contact as ‘instantaneous’ and dependable to ‘one second of time’. But other observers did report a black drop effect, such as Joseph Baxendall in Manchester, who perceived the planet as ‘decidedly egg-shaped’ at contact.18 By 1868, growing interest in the approaching transit of Venus brought ‘every possessor of a telescope in England’ out to observe the transit of Mercury on the morning of 5 November. At Greenwich, six observers were stationed to observe egress. In a trial run, the observers were to time the moment of contact as if observing the transit of Venus. The results included descriptions of various kinds of distortions. Some were very mild. For example, Stone, observing from an enormous new refracting telescope known as the ‘Great Equatorial’, reported a ‘fine ligament’ just before contact. All together, the observers gave no consensus on the nature of the black drop effect. Of the twenty-one observations of the Mercury transit published in the Monthly Notices of the Royal Astronomical Society, nine reported a distortion, three reported no distortion, and nine could not say due to ‘boiling’ of the sun’s limb or other disturbing conditions. In addition, there were three reports of a ring of light seen round the planet, attributed to Mercury’s atmosphere, which disturbed the view of contact. Most discouraging of all were the time recordings of contact. Observers side-by-side had called ‘contact’ at times differing by as much as eleven seconds.19 Stone’s answer was to reinforce the need for strict uniformity in all aspects of observation: instruments and instrument settings, training procedures, and above all observers whose attention would be directed at what he called ‘real internal contact’ – formation of the drop at ingress or break of the drop at egress – as the chief points of interest. Airy, following Stone, also believed that the contradictions and inconsistencies evident in the Mercury observations could be overcome. Thus, initially at least, the British plan in 1874 would look very similar to the plans of the 1760s. In other countries, the traditional contact method was considered much more dubious. For Newcomb and the American Commission, the results of the 1868 transit of Mercury were taken as one major reason to seek

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alternative methods. Another reason for concern – to be discussed below – was the recent confirmation of the existence of a solar atmosphere – the photosphere – and new research into the magnitude of its fluctuations. A variable and dense solar atmosphere might explain the reportedly complex nature of the visual phenomena during contact.

The Transit Proposal in Parliament Whatever the Royal Astronomer demands, the Admiralty assents to; and the Treasury, without a word of objection, grant the money. The Irish Times (Dublin), 9 December 1874

Just around the time of the Mercury transit in 1868, the state science debate (introduced in Chapter 2) gained momentum. Fears of a slipping industrial supremacy were fuelled by the Paris International Exhibition of 1867, in which Britain’s poor performance seemed to catch everyone by surprise. Concern grew that French and German systems of technical and scientific education were outperforming those of the British. In 1868 a special parliamentary committee was formed to look into possible inadequacies of the British system.20 In 1870, a Royal Commission, headed by the Duke of Devonshire and chaired by Norman Lockyer, was formed to consider the issue of science in Britain more broadly. In the spirit of the reform movement of the 1830s and 40s, the Devonshire Commission’s 1875 report would advocate once again an overhaul of education. It would also argue strongly for the foundation of national laboratories, larger research grants to private scientists and a permanent Ministry of Science and Education. Central to the Commission’s concerns was the idea that a particularly British tradition of relying on privately-funded science was now restricting progress. Commission member Alexander Strange argued: Scientific research must be made a national business … the point at which science in most of its leading branches has now arrived … is such as to need for their adequate treatment, permanent, well-equipped establishments with competent staffs, worked continuously and systematically. Lord Derby has truly described it as a case in which what is ‘everybody’s business is nobody’s business’. We must make it somebody’s business. We must make it the State’s business. We have tried individual enterprise, which so many hold to be all sufficient. There is more individual enterprise in England than in any country in the world, and yet we are being rapidly outstripped by nations who, though they encourage private exertion, are wise enough not to rely on it, but to establish a system free from caprice.21

It should be noted that if the Commission’s recommendations were carried out, some of the committee members were set to benefit personally. Strange, along with other Commission members such as Lockyer, was himself lobbying for a new astrophysical laboratory to be built in London. In this sense, aspects of the

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Devonshire Commission’s proposals posed a direct threat to Greenwich’s position within the government. Airy’s views on the subject, in which he argued against public funding of science, should probably be understood in this context. This astrophysical laboratory would never be built. In fact, most of the Commission’s proposals went nowhere. The only concrete effect was the introduction of an annual grant of £4,000 in 1878 that was to be administered by the Royal Society.22 This was to be the most substantial regular form of state funding of science for another two decades.23 In this sense government funding of science remained relatively unchanged at least until the foundation of the National Physical Laboratory in 1899. Some historians have thus concluded that, as Cardwell put it, ‘the climate of opinion was distinctly chilly for science’ and would remain so until the turn of the century.24 However, as has been discussed above, within this chilly climate major regions of scientific work remained active under the shelter of the Admiralty. The transit of Venus enterprise was one of them. Airy proceeded to plan the expeditions and observation stations according to plans drawn up in 1868. These plans proposed five observation regions to be distributed in the northern hemisphere around Hawaii and Egypt and in the southern hemisphere around Kerguelen, New Zealand and Rodriguez (see Figure 3). The first step was to find out how

Figure 3. Map showing the regions in the world where egress (the left-hand curve), ingress (the right-hand curve) and the entire transit (the intersecting region) were visible. The place names indicate the locations of the major stations. By G. Tupman, in The Engineer, 2 April 1875, p. 223.

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much the research programme might cost. This was the job of the Hydrographer’s Office, which estimated that both 1874 and 1882 expeditions would cost at least £60,000.25 The second step was to obtain funding from the government. This meant that a proposal, probably written by Airy, was read to parliament by the First Lord of the Admiralty. Although state funding of scientific research was a contentious issue in parliament and in the press at this time, the question of whether or not the government should fund these expeditions to measure the sun’s distance was never debated. Apparently the transit of Venus expeditions were seen as the kind of thing that the government must support. The enterprise would balloon without resistance into one of the state’s most expensive pure science ventures of the nineteenth century. Hugh Childers, First Lord of the Admiralty, introduced Airy’s plan for the 1874 transit expeditions to parliament in August 1869. At that time, Childers was in the process of radically overhauling the Admiralty’s administration. He had abolished the Board of the Admiralty, and was trying to squeeze the annual budget to under £10 million, something he finally achieved in 1874. According to some historians, the changes he made in the years 1868–71 led directly to what has been called the Admiralty’s ‘dark age’ of the 1870s, a period of ‘extreme economy’, poor decision-making, and a lack of financial control and accountancy.26 Reaction to technical changes came slowly and was, and as some historians have argued, often misdirected. Some military historians blame this on an inherently ‘conservative’ mindset of military men, while others believe it is due to the inherent complexity of the problems that the military faced. For example, around the time of the 1874 transit, one of the greatest technical predicaments facing the Admiralty was the threat posed by the locomotive torpedo, the technology having been secretly bought from Austrian engineers in 1871. To consider the issue, a ‘torpedo committee’ was formed in 1873, and it concluded that, in order to maintain naval supremacy and protect seaborne trade, the Admiralty’s priority must be directed at torpedo offence and defence strategies. But, under the financial constraints of the 1870s, the radical changes that this would have entailed, such as implementing new hull designs, were impossible to meet. Since the navy did not enter any wars for another three decades, the ineffectiveness of the 1870s did not have any dire results, but it has left historians wondering what the outcome of the narrowly averted war with Russia in 1885 would have been had it come to blows.27 The transit programme avoided being squeezed out during Childers’s reorganization (although the ramifications of Childers’s policies may have contributed to the serious financial difficulties the programme would later encounter). Childers introduced the enterprise to parliament in the following terms:

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The Transit of Venus In the year 1874 the transit of Venus will give the opportunity of carrying out one of the most remarkable investigations that can be made in connection with astronomy. The only method of ascertaining the distance between the Sun and the Earth, or, more correctly speaking, the horizontal solar parallax, is to observe the transit of Venus over the sun’s disc, which will occur in 1874, for the first time after the transit observed by Captain Cook during the last century … The amount is small, while the object is of great scientific value.

He then asked for an initial budget of £10,500, and requested that a letter announcing the transit proposal be sent to Queen Victoria, in order to receive her blessing.28 It is interesting that the budget of £10,500 – much larger than any previous grant for a single astronomical research programme – was proposed and accepted as a small amount. But in comparison to the Admiralty’s £10 million budget, that is what it was. The figure of £10,500 was based on a budget that only accounted for costs up to 1874, and it only referred to the costs of instrument construction. The question of who was to pay for the remaining overheads – staff, supplies, transport, data analysis and printing – would later become an issue between Greenwich and the Admiralty. In a move that should now be familiar, Childers’s invocation of Captain Cook placed the proposal in a patriotic light that played on historical pride; it implicitly suggested that the nation’s duty was to continue in the footsteps of the country’s most famous navigator. The transit of Venus – and it seems the British self-understanding of their history of astronomy in general – had a special historical resonance. The prestige of scientific expeditions (the same that Babbage had complained about in the 1840s) also added extra weight to the value placed upon the transit enterprise. Of course Childers’s claim that that the transit offered the only way of measuring that distance was certainly not true. Among astronomers at least, it was understood that a number of other methods were giving promising results. But among MPs, Childers’s exaggeration of the importance of the transit method was accepted without question. That may be a sign of the Admiralty’s sway over matters related to science, or it may be due to the absence of scientific men within parliament, or it may simply signal a broad acceptance of the transit enterprise as a matter of state science. Over the few decades of the transit programme’s lifespan, MPs would begin to express concern over the lack of ability within parliament to understand the aims and products of government-funded science. This subject will be picked up again in Chapter 4.

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The International Picture: Transit Programmes Abroad The early 1870s saw major changes in Europe’s political landscape. Italy was unified in 1870. Germany was unified in 1872 after the Franco-Prussian War. In economic terms, Britain was still the leading industrial nation, producing nearly a third of the world’s manufacturing, while the United States produced less than a quarter and Prussia only 13 per cent. But it was clear to all that the landscape of global influence was shifting. The British stance of economic superiority appeared to be increasingly vulnerable. That sense of vulnerability had prompted the Devonshire Commission and other movements to reform science funding in Britain. And the changing landscape that prompted it would be mirrored in the international competition that grew to surround the transit of Venus. In 1869 the governments of France, Prussia and Russia announced funding for transit of Venus expeditions. As in Britain, the significance of the projects would be shaped by each country’s practical interests as well as rhetoric about its history of science, its current world standing and its future. Russia’s programme was directed by Otto Vasilevich Struve, grandfather of Otto Struve, at the lavish Imperial Observatory of Pulkovo in St Petersburg.29 At a time when the Tsarist regime was threatened by populist movements, the transit was represented, as Simon Werret puts it, as ‘the purest of pure science, with no connection to the imperial topography that [the expeditions] were clearly intended to contribute to …’.30 In France, a commission had been formed by the Académie des sciences, with funding from the Ministry of Education. It would be directed by the chemist Jean-Baptiste Dumas. In Prussia the Berlin Academy organized the enterprise, which was led by Arthur Auwers at the Berlin Observatory. Preparations in both of these countries, however, would be sidelined by the Franco-Prussian War in 1870–2. The siege of Paris in 1870–1 had a major effect on science within Paris, including transit preparations. During the war, science was seen as a key resource, especially with respect to the city’s ability to withstand the siege. Afterwards, there was an intensification of nationalistic claims for science in both countries, and funding for science across the board would increase.31 The United States, rebuilding after the devastating civil war that ended in 1865, established its enterprise in 1871 at the United States Naval Observatory in Washington, DC. The proposal of spending $100,000 of government money was received more cynically in Congress than in the British parliament. The New York Times reported one congressman’s objection that: If Venus wants to transit across the face of the sun let her transit, provided the sun has no objection. It is none of our business, and I object to being taxed, or to having the people taxed, to enable scientific sharps to go half round the world, to watch her eccentric operations.

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To this the New York Times reporter commented in the same cynical tone ‘… it seems to me our astronomers might be indulged in a little pleasure excursion of this sort once in a hundred years …’.32 Yet, despite some cynicism and criticism from politicians and the press, the United States’ transit programme would grow to become one of the largest in 1874.33 The major new role played by the United States, in comparison to its small presence in the transit activity of the 1760s, is perhaps one of the most dramatic shifts of the political-scientific landscape of transit participation over the century since the last transit of Venus. ‘The Americans, as usual, have endeavoured not to be surpassed by any nation’, wrote the Irish Times, expressing the common view that the United States was out to prove itself on the world stage.34 Another major shift would be the comparative absence of Dutch and Swedish activity. The Netherlands, a major presence in the 1760s, would organize just one expedition to the French-occupied island of Reunión. Sweden, which had more expeditions than Britain in 1761, would send out none. Two newly-formed nations, Italy and Mexico (a re-established republic after the war against French intervention ended in 1867), announced funding for transit expeditions; in new countries such as these, participation in the transit was a particularly strong source of national pride. As the introduction to the Mexican report on the expedition put it: ‘The year 1874 inaugurates a new era in our history. The Mexican nation has been represented in the grand scientific contest surrounding the transit of Venus across the disk of the Sun.’35 Last but not least, perhaps true to British amateur tradition and the Victorian era of the grand amateurs, Britain also produced the only major privately-funded programme, run by Lord Lindsay, James Ludovic Lindsay, third Earl of Crawford. Lindsay and his assistant David Gill conducted research related to the transit at Lindsay’s Dun Echt observatory in Scotland. They would establish a major station at Mauritius, and would play a key role in establishing the longitudes of dozens of transit observation stations.36

Situating the Observation Stations Just as in the 1760s, press interest in the 1874 transit of Venus enterprise began with a debate over the quality and interpretation of transit visibility maps. These maps are instrumental to determining the arrangement of observation stations. Before turning to that debate, we should consider what hangs on the choice of observations stations. The transit of Venus method depends on comparing observations of the transit from two distant points on the earth (see Figure 1 above). The distance between stations can be achieved in different ways, but the greater the latitudinal distance between the stations the more accurate the result should be. Airy

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initially thought that the visibility of the transit of 1882 would allow for better station arrangements than in 1874, and at first made the case that resources should be directed towards the ‘peculiarly favourable’ transit of 1882.37 But in subsequent papers in 1864 and 1868, Airy reversed a number of his initial positions.38 More detailed maps of the transit visibility, drawn with new data from the Nautical Almanac Office, caused him to question the clear advantage of 1882, and to rethink the station arrangement. Stations could be arranged according to two different methods. In ‘Halley’s method’, also known as the ‘method of durations’, the original system described by Halley, the arrangement would be based on two or more distant stations at which the entire duration of the transit would be visible. At each station, the start (ingress) and finish (egress) of the transit would be carefully timed. From the perspective of the stations in the north, the planet would be seen crossing closer to the sun’s equator (in the case of the 1874 transit, since Venus crosses the northern hemisphere of the sun), and from the perspective of southern stations, the planet would be seen crossing farther from the equator. Hence the duration of the transit would be longer at the northern stations than at the southern stations. This difference in durations would provide the foundation for calculating the parallax of Venus, and from that the parallax of the sun. According to ‘Delisle’s method’, described by him in 1760, two or more distant stations would be chosen where only the ingress or the egress of the transit was, necessarily, visible. Again the absolute time (i.e. the local times translated to Greenwich time) of the ingress or the egress would vary depending on the location of the stations, and these differences, together with a precise knowledge of the longitude and latitude of the stations, would give the basis for calculating the solar parallax. Different station configurations based on Halley’s method and different station configurations based on Delisle’s method were capable of producing more or less accurate results. Airy had originally argued that Halley’s method in 1882 would offer the best circumstances, but after consulting the new visibility maps in 1868 he revised this plan and proposed using Delisle’s method in 1874. The quality of these maps, and of Airy’s plans based upon them, was soon called into question by the astronomer and popular writer Richard Anthony Proctor. After graduating from Cambridge in 1860 Proctor had initially begun to study law but later grew interested in astronomy. He published his first astronomy text, Saturn and its System, in 1865. The book was very well received by astronomers but did not generate a profit. In 1866, his family wealth was wiped out by the collapse of a New Zealand bank, and from then on his science writing became a crucial source of income. In all he would write nineteen titles before dying in New York City in 1888. At his death he was one of the best-known science writers of the time.39 ‘It may certainly be said of

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Mr. Proctor’, said his obituary in the Monthly Notices of the Royal Astronomical Society (MNRAS), ‘that he has succeeded in interesting a larger public in the science of astronomy than any other man’.40 His career would be given a major boost from the publicity generated by his critical and extensive (lasting over ten years) coverage of the transits of Venus. Proctor’s involvement began in March 1869, when he reported in a short MNRAS article that, by applying ‘geometrical tests’ to the maps in Airy’s articles, he had discovered some inaccuracies.41 Three months later, Proctor presented his own maps of the upcoming transit visibility.42 Proctor’s maps were based on the same Nautical Almanac data as Airy’s but were more detailed and more carefully drawn than Airy’s had been. Maps were to be a speciality of Proctor’s; his later astronomy books would feature original maps of stars, planetary terrains and the solar system. As the Edinburgh Review would later remark, Proctor supported his argument in the matter by a method in which he is particularly skilled, namely, the diagrammatic or pictorial representation of the conditions of the question … These maps were constructed by a large expenditure of industry and ingenuity …43

Basing his critique on these maps, Proctor called into question some of Airy’s plans for the observation stations for the transit of 1874. His argument was that a particular station configuration for Halley’s method in 1874 was the optimal station arrangement for determining solar parallax. ‘The best southern station taken in conjunction with the best northern station [in 1874] will give a difference of duration of no less than 36 1/2 [minutes]. The maximum of difference in 1882 will be about 28 [minutes].’44 Crucially, this station configuration depended upon locating an observation station as far south towards Antarctica as possible – to the extent that Proctor was suggesting placing observers on islands the existence of which were up for debate. Proctor’s criticisms of Airy’s plan were visible and vocal. In all, he published six articles on the subject in the 1869 volume of the MNRAS, more than any other author on the subject.45 Airy, however, apparently felt that Proctor’s work did not require a public or official reply. At this point, private correspondence between the two was brief; Proctor was cordial and apologetic and Airy only made the slightest attempts to defend his plans.46 Nothing immediately came of the debate, but it would return in a few years and generate the first wave of public interest.

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Britain’s Scientific Honour, the Press and the Airy-Proctor Debate In the early months of 1873, the press began to take an interest in the transit of Venus, and its attention was first drawn (most likely by Proctor himself ) to the debate between Proctor and the Astronomer Royal. The London Spectator’s first article about ‘The Approaching Transit of Venus’ on 8 February 1873 begins: An important natural phenomenon will occur before long, and there is some fear that this country – though the Government has been very liberal – will suffer serious discredit from the manner in which the phenomenon is to be observed. There is still time, though not a day to spare, to avoid this result; and it is chiefly with the hope of commending the matter to the attention of all who can help to avert national discredit that we submit the facts of the case to general attention, while time still remains for action.

It then gave a brief history of Britain’s preparations, placing emphasis on the initial plan for sending an expedition to Antarctica in 1882, on the discovery that the transit of 1874 was better for Antarctic observations, and the ‘singular result’ that followed: The author of this correction was almost unknown to the astronomical world (three years before he had been altogether unknown). It was otherwise with the author of the mistake. Ninety-nine persons out of a hundred would have formed but one conclusion on the subject, if the correction had been quietly ignored. This, however, was not what actually took place … this is a question very seriously affecting the scientific credit of this country … To this country specially falls the duty of seizing the opportunity, – the opportunity, namely, of making absolutely the most effective observations for the determination of the sun’s distance possible during an interval of two hundred and thirty-five years. What will be said and thought of the science of this country, if, hereafter, it must be recorded that the opportunity was missed through an astronomical blunder, and that when the blunder was indicated four precious years were allowed to elapse, during which nothing was done to replace an impracticable scheme … Twelve years of error followed by four years of apathy …47

In essence, the article takes up Proctor’s argument to use Halley’s method and send an observation to the Antarctic coast, further south than Airy or the Admiralty had been planning. The question of whether or not it was necessary to send a station to the far south was transformed into an issue of national scientific honour. Five days later came a lengthy and technically detailed article on ‘The Coming Transits of Venus’ in The Times of London. Very similar in tone, The Times also described the development of the English transit programme in a form that must have been very satisfactory to Proctor. Here, unlike in the Spectator, ‘Mr. Proctor’ and ‘Sir G. Airy’ are named as the primary characters in the

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‘unfortunate incident’ that was ‘far more surprising than even the mistake of 1769’. The article dwelled on the crucial role that the construction of accurate maps played in determining the status of events around the globe, and noted the superiority of Proctor’s maps. If the Astronomer Royal, ‘who the editors do believe to be the greatest there has been since Bradley’, had thought his ‘great reputation is justification for silence on the issue’, the editors caution him to think again: ‘Even Newton was not infallible … We have had sufficient proof in later times that great names are no guarantee of accuracy.’ Taking a dig at the Neptune discovery debate, the editors noted: One would think a matter of this kind, involving no mathematics of a high order like the discovery of an unseen planet … could hardly be a subject for dispute between mathematicians; or at least, that if an error was alleged, it would be settled and acknowledged one way or the other in a week.48

But this was not a mathematical dispute; Airy never denied that a station on Antarctica would meet the optimal conditions for the station geometry. The issue was about how far south the expeditions could or should actually go. It was a dispute about practicalities versus ambition. If anything, the debate reveals the clear limits of Airy’s ambitions regarding the transit enterprise. Not surprisingly, the newspaper articles roused the Admiralty’s interest in Proctor’s claims. Both The Times and the Spectator made indirect references to the shame that would be faced by the Admiralty if any uncorrected errors led to the failure of the expeditions. The day after the article in The Times was published, the Secretary of the Admiralty wrote to Airy asking whether ‘the articles in question are founded on fact’.49 Airy’s reply was printed in the next issue of the MNRAS. Acknowledging that the newspaper articles were based almost entirely on Proctor’s article from June of 1868, he began with an appreciation of the ‘great clearness and unquestionable value’ of Proctor’s maps. Then, drawing the line between what is possible and what is practical, he defended his articles of 1857, saying that practicalities weighed more heavily on his thoughts than they had on Proctor’s, and asserting defensively that nothing Proctor had raised had been unknown to him. The differing conclusions that he and Proctor had reached sprouted from the divergence of his more ‘eclectic’ consideration of the problem, including the impact of extreme weather conditions in Siberian and Antarctic stations, the benefit to the accuracy of the final result of using fewer observations and more calculations of longitude (as would be done with Delisle’s method), and Proctor’s sole interest in ‘straining to the utmost the idea of separating as far as possible the northern and southern stations, and considering nothing but their geometrical relations’.50

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The subject was also taken up in parliament, where, on 25 March, MPs asked whether Halley’s or Delisle’s method was to be used and whether Britain was acting in concert with Russia.51 (The latter was probably connected to the impending wedding of Queen Victoria’s second son to the daughter of Emperor Alexander III.) A few days earlier, Airy had been informed that the question was to be raised in the House of Commons, and, although Airy was not credited, it was his reply that was read verbatim by the First Lord of the Admiralty in response. Airy explained that at three of the British stations, Kerguelen, Christchurch and Rodriguez, the entire transit would be visible, so Halley’s method could be used with data from those stations, but that in his opinion (and, he pointed out, in the opinions of the Germans, French and Russians) Delisle’s method was ‘greatly superior’, and he remained focused on obtaining the precise station longitudes that that method would require. Proctor continued his call for the Astronomer Royal to acknowledge the value of Halley’s method and to add stations in the Southern Ocean. A lengthy response to Airy’s letter to the Admiralty was published in the same volume of the MNRAS, in which he concluded: I cannot but express my conviction that it will be little less than a national calamity, as assuredly it will be scientifically most regrettable if any considerations, either of convenience or of personal dignity on the one hand, or of false courtesy on the other, should lead to the loss of opportunities which will not be again available for many years to come.52

In the next few months Proctor published eight more articles on the subject of the transit in the MNRAS alone, reiterating his arguments in various ways. One article was a pointed criticism of the Admiralty. In this article he published his own charts of the Antarctic, showing the best station locations to be on small Southern Ocean islands that did not appear on Admiralty maps. These charts were drawn from several ‘ordinary atlases’ rather than those of the Admiralty. Proctor provocatively asserted that Admiralty information was biased and therefore unreliable: ‘one naturally feels doubtful about Admiralty statements [about the existence of certain islands], which would appear to be variable according to official requirements’.53 Proctor also had the support of some prominent astronomers, such as John Couch Adams, Professor of Astronomy at Cambridge, who at this time was writing to Airy urging him to go for an Antarctic station. Proctor also wrote to Airy for the same reason, letting him know that he intended to get the Board of Visitors to Greenwich to consider the issue. Airy’s reply was harsh and dismissive; he sought to remain above the whole affair: ‘The printed letters in the Spectator … and in the Times were unexceptionable … I do not think that any good comes from letters of this class, and I should not imitate them.’54 Nevertheless Proctor

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succeeded in getting the Board of Visitors to Greenwich to raise the issue of an additional southern station. Airy was thus forced to formally ask the Admiralty to consider the issue. The Admiralty appears to have been unmoved by the concern for the nation’s scientific honour. The brief reply stated: The probabilities of finding any additional and suitable and accessible Stations for the observation of the Transit of 1874 in the Antarctic or Southern Oceans appear to them to be with one exception so remote as not to justify them in dispatching a Ship of War on such a special Mission.55

The Admiralty did however agree that if the Challenger, which would be in the area to deposit a transit expedition at Kerguelen Island, found any other suitable islands, then the question might be considered again. This concession was sometimes relayed in the press as a victory for Proctor. Officially, that put the entire debate to rest. June 1873 saw the zenith of Proctor’s influence on the transit enterprise. Around this time, some members of the Royal Astronomical Society began to turn against Proctor. In particular, it was Proctor’s attack on the credibility of the Admiralty that angered members such as Warren De La Rue.56 Proctor, who was then the editor of the MNRAS, published the thick supplement to its June edition, which contained nothing but his transit articles and maps. A formal complaint was submitted. It was asserted that Proctor was abusing his position as editor. He was soon forced to step down, but even that did not end the drama Proctor had stirred up.57 The Airy-Proctor debate divided the Royal Astronomical Society community. Those who tended to agree with Proctor felt that the debate highlighted the general problem of the Astronomer Royal’s and the Admiralty’s unchecked authority. Those who tended to agree with Airy painted Proctor as an opportunist and the controversy itself as overblown. This division became problematic when Proctor was nominated for the 1872 gold medal of the Society. In an unprecedented retreat, the nomination was subsequently withdrawn and it was decided that no medal would be awarded for that year. Proctor, of course, suspected this was Airy’s influence at work. The issue of Proctor’s gold medal was also tied up with the recent proposal by Strange, Lockyer and De La Rue to found a national solar observatory, which Proctor (and Airy) vocally objected to. Proctor thus blamed both Airy and Strange for having lost him the medal. Strange and Airy, however, claimed that Proctor’s initial nomination was illegal because not enough Council members had been present at the meeting when it was passed. The entire episode ended with the resignation of Strange, Lockyer and De La Rue from the Council, closing a turbulent period for the Society, which had also been split over the Devonshire Commission’s proposals.58

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In the autumn of 1873 Proctor set off on a lecture tour throughout the United States, where he continued to publish on the transit in articles that typically discussed the advantages of the American approach and the deficiencies of the British one. Proctor’s criticism of the British programme made him popular in the United States; he became a regular contributor on the transit of Venus to The New York Times.59 The American press, however, was not unanimously friendly to him. In The Nation’s review of Proctor’s lecture tour (after he had returned to England), the editors were especially harsh: Now that the sober truth can no longer harm Mr. Proctor, we may point out the exaggerated importance which he holds himself, three of his biographers in as many of our monthly magazines, and any number of news reporters, have attributed to a supposed battle about the transit of Venus which he has fought and won with the Astronomer Royal. The plain fact is, that the plan persistently urged by him of occupying stations on and near the Antarctic continent is pronounced entirely impracticable by every competent navigator … and the question of Halley’s vs. Delisle’s method is of no practical moment … It is true that the suggestion of an Indian station has been taken, but we know of no prior opposition to the suggestion … and the conclusion might well have been the same had Mr. Proctor never lived.60

Indeed, the Airy-Proctor debate was most of all the springboard for Proctor’s career as an author. It did generate a lingering worry that the British programme was being outdone by other countries, particularly America. In the summer of 1874, for example, one member of the House of Lords complained: There is a prevailing opinion that this country had declined to occupy stations of importance on the ground that the attempt would be too arduous and difficult – while the Government of the United States had undertaken in the interest of science to do what the British Government supposed to be surrounded with insurmountable difficulties …61

Proctor did bring the subject of the transit of Venus deeper into popular culture than it might otherwise have penetrated. For a while in 1873 the question of the use of Halley’s method or Delisle’s method was a fashionable subject for discussion. The Edinburgh Review turned to the topic in July 1873 with a history of the subject and a review of the Airy-Proctor debate. It was the opinion of the editors that the Astronomer Royal’s views should be trusted over those of Proctor. The article also highlighted the fact that no German, Russian, French or American astronomers had joined the cry raised by ‘one single English voice’. Surely if these countries all worked together there was no need for yet another station. Siding with Airy, and entirely overestimating his cooperative spirit, the editors concluded: Proctor … not having to administer the limited allowance of public money awarded for this service, may mourn over the conception of England not standing in the

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The Transit of Venus van of the movement, or perhaps accomplishing its objects single-handed. But the Astronomer Royal, with a more cosmopolitan sense, in all probability feels that the result will no less certainly be secured under the admirable spirit of cooperation and consent that bonds nation to nation, where the noblest achievements of science are concerned.62

Here is an example of the cosmopolitan counterpoint to Proctor’s more stridently nationalistic rhetoric. The internationalist rhetoric of science was never very far removed from the subject of the transit enterprise. On this view, the aims and attitudes of science workers transcended national borders and national prejudices. The Edinburgh Review, more inclined to this view, assumed incorrectly that international cooperation was on the table. In fact, it had never even been seriously considered as an option. It was on the nationalistic side of the coin that Proctor was betting. And indeed (as we will see later on) the same would be true with Airy and his planning of the expeditions. The Airy-Proctor debate illustrates how, in Proctor’s time, science journalism was not very easily separable from the working world of science. Here science journalism was not about transmitting scientific ideas to the public for educational purposes. Rather, it was a dispute internal to the astronomical community that was put on display to the public in the hope of attracting political support. Certainly Proctor was not simply a commentator on astronomy; he was a participant in a way that most science writers today are not. In fact it is conceivable that, if things had gone a different way, this episode could have launched a career in astronomy, not in astronomy journalism. The overall situation runs contrary to expectations about how nationalism usually works: here we have a (self-appointed) representative of public opinion arguing that the government was doing too little to promote Britain’s scientific image. Patriotism does not necessarily originate out of government efforts to stir it; in this case the nationalistic framing was first pushed by an outsider. Of course, none of this is to suggest that either the MPs or Proctor, in their strenuous concern for ‘the scientific credit of our country’ had accurately captured any significant sector of public opinion. It is difficult to say whether there really was any public opinion at all regarding the transit enterprise. On the other hand, the fact that Proctor chose to frame the station debate in nationalistic terms may be taken to suggest, at the very least, that it was a generally acceptable position. Whether seen as rhetorical tools, as individual tendencies or as something else entirely, nationalistic sentiments were not lurking deep under the surface of Victorian culture. Rather, national pride was celebrated, codified and literally on display in the huge fashion for international industrial exhibitions that spanned the second half of the nineteenth century. With their intermingled message of international brotherhood and international rivalry, their medal system by which each country’s industrial power was to be easily ranked, and the political significance of

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their outcomes, the Victorian exhibition culture reflects precisely the national and international dynamics of the worldwide transit enterprise. Cardwell has argued that the international exhibitions were ‘milestones of progress’ for the public: ‘The Victorian could note, exhibition by exhibition, the advances made in the various sciences, technologies and applied arts both by his own country and by its trade rivals … They were media of communications and it was not long before this aspect became very important’.63 The transit enterprise became a site of international scientific competition through other media of communications – cheap and prolific newspapers and periodicals – which distributed messages of its rhetorical, national significance across an incredibly wide range of people. Historians of science have argued that in this period the traditional rhetoric of internationalism and science was increasingly matched by an ideology connecting science to national identity.64 This coincides with patterns seen by political historians, who have tried to show that it was only in the late nineteenth century that nations emerged, for the first time, as a powerful ‘imagined community’ to which people felt they belonged, producing an entirely new ideology of nationalism.65 At the extreme of this position, historian Norman Rich argues that ‘the most pervasive and dynamic ideological force in the nineteenth century was nationalism’.66 It remains unclear just how pervasive – and just how new

Figure 4. The frontispiece to the bound annual of Punch, 1874. Reproduced by permission of the Bodleian Library, University of Oxford.

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– was the rhetoric of science nationalism that Proctor successfully co-opted but, as we will see, it certainly was not limited to Proctor or to the press. As the day of the transit, 8 December 1874, neared, the press coverage of the ‘astronomical event of the century’, would continue to grow (we will return to the subject at the end of Chapter 5).67 By 1874, eight countries were, all together, planning about seventy-five observation stations at a total estimated cost of $1 million. Scribner’s Monthly argued: ‘It may seem to some that the results to be arrived at are not worth so great an outlay, but the general voice of the non-scientific world as well as of the scientific world has contradicted this’.68 The frontispiece to Punch’s bound volume for 1874 takes as its subject the multinational spectacle that the 1874 transit of Venus would be (see Figure 4). In the illustration, transit of Venus observers are portrayed as caricatures of national personifications (Britannia and Uncle Sam are most recognizable), crowded together, peering towards the sun with various instruments, elbow-to-elbow, jostling for a view.

4 INSIDE GREENWICH: THE PREPARATIONS FOR 1874

Government observatories of the nineteenth century were not generally important sites of experimentation and research.1 Experimentation was something more likely to be found – in Britain at least – in a private observatory or laboratory. But the case of the transit of Venus would be different. Although the general plan to be followed was 200 years old, and although the basic set-up would be the same as it had for the transit of 1769 a century earlier, the astronomers preparing for 1874 faced major unknowns. During the four years between the establishment of the programme and the day of the transit of Venus, preparations would consist largely of time-pressured research and experimentation into these unknowns. The highly-refined surveillance of celestial motions that defined Greenwich astronomy would be supplemented with speculative experimental investigations into subjects ranging from conductivity in telegraphic wires to the shape of the sun to the properties of photographic emulsions. Greenwich would come to look more like the private astrophysical observatories of men such as Norman Lockyer, and in the process Airy would enlist the help of some of the most prominent amateur astronomers. The direction and scope of research was shaped by a number of issues, with the dominant concerns circling around the black drop phenomenon. In the early 1870s there also emerged new theories about the physical nature of the sun that bore directly on the black drop and other key issues, especially those relating to photography. Photography was just one of a whole new range of technologies available for making different sorts of approaches to the transit of Venus measurements, and by and large these technologies would have to be applied in new and untested ways. At almost every stage in the development of the programme there was virtually no clear agreement among the experts from different nations about the best way of proceeding. While the programmes in France, Germany and the United States were organized around commissions, in Britain Airy was the sole manager. He described his management philosophy to Arthur Auwers at the Berlin observatory in 1873: – 57 –

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The Transit of Venus The British arrangements for the transit of Venus do, in fact, rest with me. I wish they did not; but it is very difficult to act continuously with a Committee, and there is no person but myself who is really subject to public responsibility. You must therefore accept what I say as the representation of my present opinions; the ultimate actions may be affected by the intermixture of the opinions of other persons, and also by change in my own.2

In practice however Airy was deeply reliant on certain individuals whom he had come to trust, and before making any decisions on anything ranging from photographic equipment to personnel choices, he absorbed their advice. The final shape of the programme was by no means due to Airy alone. It was shaped significantly, on one side, by ‘grand amateurs’ or private astronomers and, on the other side, by military engineers. Airy looked to these two pools of local scientific talent for guidance rather than the official committees of other countries. William H. M. Christie, the first assistant at Greenwich, would be present and active throughout the life cycle of the programme. But the person who was most involved was George Lyon Tupman, a Captain in the Royal Marine Artillery, who had had a long career in the navy, starting with his education at the Royal Naval School, St Cross. He entered the Royal Marine Artillery in 1855, and joined the Royal Astronomical Society in 1863. Tupman was transferred to the transit project in early 1872, after having been at sea for the previous four years. His role as ‘head instructor’ was more like ‘chief of operations’, and he became centrally involved in all aspects of the programme’s management. In all he would spend nine years working on the transit enterprise, and this work would comprise his most significant contribution to astronomy, according to his obituary in the Monthly Notices of the Royal Astronomical Society (although he also produced some of the first measures of the velocity of meteors).3 After Airy, Tupman was the most central figure in the programme, and in many ways his involvement – he was manager, observer and calculator – went deeper than Airy’s. Tupman’s daily log of the work at Greenwich gives the best overview of what the structure of working life in the programme was like. Here, observatory-asaccounting-office might be the most apt metaphor for Greenwich. Tupman’s logs confirm what the mass of Airy’s daily correspondence in the archives suggest: Airy’s place throughout the preparations, the expeditions and the calculations was behind his desk. He managed via written instruction. His eyesight was too poor for any observing and he never went on expeditions. Airy’s growing obsession in his later years with office technology and organization has been documented by his biographers: ‘The well-told tales of Airy the hard taskmaker and fussing observatory busybody, who spent days sticking “Empty” labels on old crates, come from the last few years of his office, when the Astronomer Royal … approached 80’.4 These are the years of the transit of Venus enterprise as well;

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Airy would turn seventy-two in 1874. The transit archives contain numerous examples of Airy’s incredible secretarial fastidiousness.5 It was micromanagement at a distance the whole time, even before the expeditions had set out. The focus in this chapter will be on the role of private experts, the role of military personnel and the use of the following new technologies: photography, modelling, submarine telegraphy and precision chronometry. The most contested subject – and the subject most shaped by the strains of scientific nationalism harboured at Greenwich – was the new technology of photography. Here we see how that ideology, commonplace as it may have been, would directly affect the design of the British programme. By 1870 photography was everywhere in Victorian culture. Portrait studios, hawkers of cartes de vistes, shops providing affordable equipment, photographic schools and societies, and racks of publications devoted to all things photographic were all commonplace. Like the railroad and the telegraph, photography was one of the new technologies that infused all of Victorian society – including Victorian science – with a distinct sense of modernity. What effect did the invention of photography have on the sciences? A series of recent case studies has examined that issue. One influential study has focused on the production of photographic atlases for disciplines such as anatomy, botany and geology. The authors argue that as ‘mechanical objectivity’, provided by photography, overtook the older ideal of ‘true to nature’ illustrations, provided by the skilled draughtsman, the concept of objectivity was itself ‘moralized’ in ways that continue to affect how we define objectivity today.6 However, other studies have suggested that the appeal and perceived potential of photography as an instrument of science was very different from the ‘mechanical objectivity’ that these authors have identified.7 Often the value of photography was more like that of a microscope or a telescope; it could make visible things that were too fast, too small or otherwise beyond the limits of human vision. Most importantly, it did so in a way that avoided the problematically individual experience of seeing through the telescope or microscope. Photography enabled people to visually investigate, as a group and at leisure, a lightning bolt, the infrared spectra, a possible trace of a spirit or a colony of bacteria. This perspective also links to the subject of objectivity, but in a different sense, one that rests on the role of communal assent rather than on any ideals of mechanical image production. In the case of the transit of Venus, the perceived value of photographic data would stem from yet another sense of objectivity – one that in this case is linked to the much larger quantities of data obtainable with photography than without it. As we will see, if astronomers saw a unique objective value in photographic data, this derived from contemporary ideals of statistical rather than mechanical objectivity. The statistical value of photographic data was just one of a number of photography’s

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potential assets. Yet there were as many – if not more – reasons against the use of this poorly-understood and controversial new technology.

Warren De La Rue and the Photographic Plan One small but spectacular entry on view at the Great Exhibition of 1851 was a photograph of the moon taken by Henry Bond at the Harvard College Observatory. Photography was then only a few decades old. This image was among the very first sharp photographs of the moon. Here its pockmarked surface was revealed in beautiful detail, and this permanent image could be enjoyed at any time without taking turns to look through a telescope. One visitor who was deeply impressed by Bond’s photograph was Warren De La Rue, part of the family of stationers that owned the giant firm De La Rue & Company. He was active in the family business, and from 1865 he would hold the post of Engraver to the Board of Inland Revenue and Warrants, where he was closely involved in the printing of postage stamps.8 In the 1840s, De La Rue had begun private research in chemistry and electricity. After seeing Bond’s photograph in 1851, as he told it, he turned to astronomical photography. De La Rue would become the leading figure in astronomical photography in Victorian Britain, and he would be the primary motivator and designer behind Britain’s very ambitious plan to measure the distance to the sun using photographs of the transit of Venus in 1874. The plan was ambitious because it would require taking astronomical photography in a new, untested direction: towards measurement. Prior to the 1870s, astronomical photography had been used primarily as a tool of visualization in solar physics and spectroscopy. Photographs like Bond’s had helped astronomers to chart the terrain of the moon and capture the surface features of the sun. But in the transit of Venus, photography had to provide not surface details or visual evidence for qualitative debates but an accurate representation that could be measured in lieu of measurements taken from nature. Photography in the transit of Venus was to be very much a step into untested waters. Very generally, the photographic plan – for all countries that would use it – was to calculate solar parallax from measurements, taken from photographic plates, of the distance between the centre of Venus and the centre of the sun. From stations in the northern hemisphere, the path of the transit would be closer to the sun’s centre, and from southern stations it would be farther. This difference between the transit path locations as measured from plates produced by northern and southern stations, along with precise longitudes and latitudes of these stations, would provide the basis for calculating parallax. So, in photographing the transit of Venus, the goal (with the exception of the Janssen apparatus, to be described below) was not to capture an image at or near the moment of contact. Rather, the method called for photographs of the planet throughout the transit,

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and one major benefit of the approach was that the moments of contact were avoided entirely. There was some precedent for using photographs as a basis of precision measurement. In 1857 – less than a decade after the very first astronomical photographs – Henry Bond captured the first photograph of a double star using the Harvard College Observatory’s Great Refractor.9 Subsequent measurements of the distance between the stars were taken from the photograph using a reading microscope and compared to measures of the same distance by telescope and micrometer. From measures of a series of such photographs, Bond was surprised to find that the probable error of a single photographic measure was actually less than with telescope and micrometer measurements. This was an exciting result and, even fifteen years later, it was held up as a prime example of the capabilities of accurate photographic measurement. It would set an important precedent for the use of photography in the transit. The solar eclipse of 1860 was the first to be extensively photographed, and it was also the first project employing astronomical photography in which Greenwich would have a hand. Around 1860 there was much debate over the nature of the bright spots of light (‘Bailey’s Beads’ or ‘solar prominences’) that sometimes appear in the corona of an eclipse. Some astronomers argued that these prominences extended out from the sun and were part of it; others strongly disagreed. De La Rue came up with a plan to address this debate with photography. Airy secured £150 from the Admiralty, and De La Rue, as principal photographer, provided a further £450.10 ‘The main object of the [eclipse] observations’, wrote De La Rue, … [is] to ascertain whether the luminous prominences are objective phenomena belonging to the Sun, or whether they are merely subsidiary phenomena, produced by some action of the moon’s edge on light emanating originally from the Sun. If the luminous prominences are attached to the Sun, it is evident that they would continually change their positions with respect to the moon’s centre as the moon moved across the solar disc.11

By measuring the location of prominences relative to the centre of the moon as seen from different stations, De La Rue was able to give ‘convincing proofs’ that the prominences were attached to the sun.12 The ability to provide such detailed knowledge of the solar surface opened entirely new avenues for astronomical and physical research. De La Rue’s eclipse research shifted these debates from drawings and verbal descriptions of eclipse observations to quantitative mapping studies. This early work in measurement photography earned him awards (the Royal Astronomical Society’s gold medal in 1862 and the Royal Society medal in 1864) and fostered his reputation as Britain’s ‘foremost pioneer of celestial photography’.13 And the model of close collaboration between Greenwich and

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De La Rue that was so successful in the solar eclipse expeditions would form the basis of a similar collaboration for photography in the transit of Venus. One last important precedent for precision astronomical photography from this time is the sunspot research conducted at Kew Observatory from 1860 to 1873. Conducted by De La Rue, Balfour Stewart and Benjamin Lowey, the project aimed to measure the movements and dimensions of sunspots over an extended period. At the time, it was the most rigorous astronomical study using photographs in Britain. The Kew study, like Bond’s double-star study, would be referenced in both British and American articles on the potential use of photography in the transit of Venus. The Kew study was particularly relevant because it relied on measurements of the sun’s diameter, which would be central to the transit programme as well. At Kew, sunspot movement was recorded by measuring each day the location of the centre of sunspots relative to the centre of the sun. The transit work would measure the distance to the sun by recording the location of the centre of Venus with respect to the centre of the sun as seen from different observation stations. Although all of this early work with photographic measurement was an important starting point for the transit programme, none employed measurement to the degree of precision that would be required in the transit. There remained a significant amount of uncertainty about the transit photographic plan. De La Rue, however, was highly optimistic. He began lobbying for it as early as 1868. In support of his plan, he went so far as to assert that the conditions for transit photography were actually better than those of an eclipse and were no more challenging than the daily sunspot research at Kew. He even argued that that the transit photographic measurement would be ‘far more easy’ than eclipse measurements and that, while an eclipse lasted only minutes, the transit, lasting up to four hours, would allow for hundreds of photographs to be taken without any of the ‘strain on the nerves’ that accompanies eclipse photography. He reckoned that the distance between the centre of the sun and the centre of Venus could be measured to within one second of arc ‘by means of a few pictures’ and to within a quarter of a second of arc if a sufficient number of photographs were obtained.14 It is important to point out here the role that the quantity of photographs obtained was expected to play in improving the precision of the photographic measurements. This was a reflection of contemporary error theory, according to which errors in measurements, if non-systematic, would be random and would therefore, in a large data set, tend to cancel each other out.15 On this view, the larger the data set, the lower the residual error, so as many observations as possible should be used. Thus one major advantage of photography was that hundreds of ‘observations’ of the transit of Venus could be taken at each station, compared to the two or three eye-observations. This was also the primary reason why De La Rue and others expected to obtain a high

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degree of precision with photography. In order to obtain a measure that would improve current knowledge of the sun’s distance, the distance between the centre of the sun and the centre of Venus would have to be measured with certainty to within 0˝.25 seconds of arc (measuring in ‘seconds of arc’ from the photographs involved translating the arbitrary scale used to measure the photographs into seconds of arc, as if the measure was taken from telescopic observations). Airy was sceptical about the idea. It was not that he was against photography in principle; he had been very impressed by Bond’s double-star measures of 1857 and had optimistic views on the future of astronomical photography. Writing to Bond in 1857, he imagined photography being employed for ‘the next great advance in astronomy – the self-registration of [stellar] transits and zenith distances’.16 However, in the case of the upcoming transit, it was the unprecedented level of precision required, combined with the possible presence of systematic errors in the photographs – which could not be averaged out – that made Airy cautious. Even after the Board of Visitors to Greenwich, which included De La Rue, recommended in the annual June visitation of 1869 that ‘steps be taken’ to use photography in the transit of Venus, Airy did not include photography in the initial transit budget sent to Whitehall and parliament in August of that year.17 De La Rue persisted. He sketched out a plan to employ instruments similar to the photoheliograph used for the sunspot research at Kew Observatory.18 De La Rue had also used the ‘Kew photoheliograph’, as it was known, in the eclipse of 1860. Built for the Kew Observatory Committee, it was designed by De La Rue and made by the London optical firm Dallmeyer.19 On De La Rue’s suggestion, the instrument would eventually – and controversially – become the model for the British transit of Venus photographic instruments. De La Rue discussed his plan with Airy throughout 1870, but Airy remained unconvinced. Ultimately De La Rue used his position on the Board of Visitors to Greenwich to push the plan forward. In the annual June visitation of 1871 the Board resolved to apply – independently from Airy – to the Admiralty for funds to add a photographic arm to the expeditions. This was not exactly an assault on Airy’s leadership, as the Admiralty in turn asked Airy for his opinion of the plan.20 While preparing his reply, Airy prodded De La Rue for clear advice: I will only ask you one final question upon the possible accuracy of reductions of the photographic records in the transit of Venus. Probably eye-observations (if we can get them) will be trustworthy to 0˝.14 or 1/13000 of the diameter of the sun, or to 1/250 that of Venus. Can you trust the interpretations of photographs to accuracy comparable to this? You know you are the only person whom I can trust in photography and I have to make the best report on the matter that I can, and troubles like these will fall upon you.21

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In reply – as Airy must have expected – De La Rue reiterated his confidence that the degree of precision required could be met. De La Rue acknowledged that he had not yet attempted a measurement to that degree of precision. Indeed, his publication on the solar eclipse of 1862 used measurements to only 0˝.5 or 1/3640 of the sun’s diameter, and the limit to precision was the same in the Kew sunspot publication.22 Yet De La Rue assured Airy that he had ‘not the slightest hesitation in saying that measurements may be depended upon now to … [0˝.12 or] 1/16000th of the sun’s diameter’.23 In July 1871, a month after the Admiralty requested Airy’s opinion on the use of photography, Airy replied:24 some of the objections to the photographic method which I formerly entertained are or may be removed, and that it may be accepted as a valuable adjunct to the system of eye-observations, with no little probability that in conceivable circumstances it may save the result of the whole enterprise.

In other words, Airy still only went so far as to endorse photography as a precaution against a total failure of the telescopic plan. The most worrying ‘conceivable circumstances’ had to do with the weather, specifically clouds at the moments of ingress or egress. Without photography, a puff of cloud passing over the sun around ingress or egress could cause a station to fail totally. With photography, so long as the sun was visible for a few minutes while the transit was taking place, potentially good data could be collected.25 For Airy, then, the photographic plan was most importantly an added security against bad weather. Along with this qualified endorsement, Airy also sent the Admiralty a budget listing the expenses for the five stations, adding to each at least two photographers and one photoheliograph. Airy did not take De La Rue’s opinion entirely at face value, as his continuing scepticism and persistent questioning of the details of the plan shows. Overall, however, Airy would display remarkable trust in and loyalty to De La Rue. Airy had given his backing to the photographic plan, and in doing so he took on De La Rue as the unofficial head of the photographic preparations. With an additional grant of £5,000, the British photographic programme was officially set in motion. The first piece of business was to get the instrument construction underway. An order was placed with Dallmeyer for the five photoheliographs. These were to be designed along the lines of De La Rue’s Kew photoheliograph, and De La Rue mentions working closely with Dallmeyer during their production. Each transit photoheliograph had a 3.4-inch aperture objective and a 50-inch focal length, giving an image of the sun that was 0.48 inches in diameter. This was then enlarged by a secondary magnifier to 3.9 inches (see Figure 5). Under De La Rue’s plan, 100 to 200 photographs of Venus in transit were to be taken at

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Figure 5. One of the photoheliographs set up in its custom-built observation hut during a trial run at Greenwich. Note the stencilling on the boards inside the hut. Reproduced by permission of Cambridge University Library, shelfmark CUL RGO/6-276 no. 18.

each station. Here, again, the quantity of images was key to the precision of the photographic measure. De La Rue also pressed for the location of the observation stations to be reconsidered. But the only change made here was the addition of a station in India, to be operated from the Madras Observatory. (This change was partly due to public pressure exerted by Richard Proctor.) Other than that, Airy resisted making major changes in order to accommodate photography. He had told De La Rue in 1870, ‘I have so high a value of the eye observations that I cannot make any shift of my own stations which would abandon that advantage’, and his opinion on this would not change.26 Reporting on the addition of photography in 1872, the editors of Nature observed, ‘The plans for photography were advanced from photographic quarters; astronomers of the exact class who were not photographers were somewhat sceptical at the outset concerning its accuracy’.27 De La Rue in fact had been given almost complete control over the entire photographic plan. He had specified the instrument design, and he would advise on the training of the observers gathered at Greenwich, and recommend tutors in photography to the observatory. Most importantly, as the construction of the five photoheliographs got underway and photographers were recruited for duty, De La Rue was called on to counter rising concerns about the design of Britain’s photographic plan.

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The Transit of Venus

Precision Astronomical Photography in the Wet-Plate Era When considering the introduction of photography as a scientific instrument, it is necessary to take into account the major developments in photographic technology, especially when thinking about the question of photographic evidence. That issue is tied into crucial technical differences between what might be called the ‘wet-plate’ era, which began in the 1850s, and the ‘dry-plate’ era, which began, at the earliest, in 1875.28 In the wet-plate collodion method, a glass plate would be dipped in a freshly-prepared photosensitive emulsion, and would be exposed and developed when still wet. The invention of dry-plate photography, in which prepared plates (and eventually films) could be stored for months before and after exposure, would transform the production of photographic media from an individual chemistry-based practice into a standardized, mass-producible commercial product. With the dry-plate process came major improvements in image quality, reliability, standardization and ease of use. It could easily be argued that it was only after this period that photography took on the connotations of mechanical image production that would become so strong in the twentieth century. When the transit photographic programmes were forming in the early 1870s, the wet-plate process was at its peak. These programmes would turn out to be one of the last – and most expensive and ambitious – scientific applications of wet-plate photography ever organized. The problematic status of early astronomical photography comes out in the debates that surrounded the transit photography programmes. Everyone agreed that the data gathered from the photographs had to be extremely accurate and precise. Newcomb described the problem in 1872: The determination of the solar parallax from measures of photographs of the sun taken during the transit is beset with this serious difficulty: that the required element appears only as a minute difference between two comparatively long arcs, much longer, in fact, than are often measured with a micrometer. In order that the solar parallax may thus be determined with a precision exceeding that attained by other methods, it is necessary that the arcs in question be measured with a precision considerably exceeding any ever attained in the astronomical measurement of an arc of similar length.29

As planning got underway, the potential obstacles to the success of transit photography were dealt with differently in each country. Often there was substantial disagreement over the best way to proceed. The cause was not only the lack of standards for the chemical and material aspects of photography but also contemporary developments in solar physics and, more generally, the inward-looking bent of the transit commissions and leaders. The result would be a total lack of coordination among the countries’ photographic programmes.

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Potential obstacles to successful precision measurement existed on three different levels, each of which will be introduced below. Problem I: Finding the Centre of the Sun In mid-September 1872, De La Rue forwarded Airy a photograph of the sun taken with the photoheliograph at the Vilnius (Wilna) University Observatory in Lithuania, where since 1865 a Dallmeyer photoheliograph similar to the Kew photoheliograph had been in use. Airy was not entirely impressed: ‘The Wilna photograph of the sun is the most beautiful that I have ever seen. But the degradation of the light to the limb is very rapid. Will there be any doubt as to the limb?’30 Since, in order to calculate the parallax from the photographs, it was necessary to find the centre of the sun, it was crucial that its outline (or limb) appeared clearly in the photographs.31 The clarity of the outline could be affected by a number of technical circumstances, but a more fundamental issue was whether or not the sun, under any circumstances, had a clear enough outline to find a centre or diameter from. One problem was the solar atmosphere, or chromosphere, the existence of which had been confirmed only three years earlier by the spectroscopic research of Norman Lockyer. A solar atmosphere of some kind had been suspected for most of the nineteenth century.32 Its depth and composition was a current subject of debate, and each theory about the chromosphere’s constitution had implications for transit of Venus photography. In De La Rue’s own research, he handled the ‘somewhat irregular’ outline of the solar limb with a specially-designed rotating micrometer.33 The instrument was a microscope fixed above a layer of plates that rotated and slid horizontally. The radius of the sun was measured by first finding the centre of the photograph, and then sliding the plate holding the photograph horizontally to the position where the edge of the sun generally coincided with the crosshairs of the microscope. Then the plate was rotated, and if the edge of the sun maintained coincidence, that is, if the crosshairs appeared to generally follow the limb of the sun, then the radius could be read off as the distance the plate was moved horizontally from the centre. In early 1872, the United States Commission for the Transit of Venus was consulting with American solar photographers on this very issue. One of the first to be consulted was Lewis M. Rutherfurd at the Columbia College Observatory. Rutherfurd had conducted extensive studies of photographic optics as applied to astronomy and had experimented with different lenses in order to correct the telescope for photography. He found no lens arrangements that were entirely free of distortion.34 In a detailed reply to a letter from the commission,35 Rutherfurd concluded with a strong caution that:

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The Transit of Venus After the photographs have been obtained, with all the precautions a careful foresight can suggest, it is important that no reliance should be placed for precision upon the apparent outline of the sun at any isolated point … Perhaps you will say, if this be true, what reliance can be placed upon the results of photography? I should answer, that the sun has no sharply-defined outline even to the eye, but, in its best state is an irregular seething, ever-restless object, utterly unfit to be the starting point for measures of precision, and that, while the eye is confined, in its attempts at measures, to some small part of the sun’s limb, the photograph of the whole sun can be placed upon the stage of a micrometer, and accurately centered with reference to the average of the whole contour, and thus escape the errors sure to be the result of local bisections.36

Thus according to both De La Rue and Rutherfurd, despite the inherent irregularity of the solar limb, accurate measurements could be made as long as the average of the whole circumference was the basis of measurement. After the transit, this would become a difficult point of disagreement between De La Rue and Airy, who, perhaps to the detriment of the programme, would not accept the utility of De La Rue’s rotating micrometer design. Problem II: Enlarging the Sun’s Image One of the most difficult problems lay in how to obtain a sufficiently large image of the sun on the photographic plate without, first, causing any distortion and, second, losing track of the scale of the image. It is on this issue that the American and British photographic programmes would be completely divided. As described above, the instrument that was to be used in the British programme had a 50-inch focal length and an enlarging lens to create a image of the sun about 4 inches in diameter. It was well known that the intermediary lens would produce an amount of optical distortion in the photograph, meaning that the image would stretch or be compressed in certain areas. In 1868, to discover whether there was a need for an error correction in the measurements made of the sunspots from the Kew photoheliograph, De La Rue had produced a series of photographs of the pagoda-shaped building at Kew Gardens, using the structure as a scale of equal parts.37 If there was no optical distortion then all of the layers of the pagoda would measure the same length throughout the photographs no matter where they sat on the photographic field. De La Rue found, however, that an image of an object formed near the edge of the field was longer than an image of the same object formed at the centre. In the Kew report, which was listing only preliminary results, no corrections were made to the measured locations of the sunspots, partly because the value was significant only if the spots were at the extreme edge of the field and partly because there was a degree of uncertainty in the measures of the scales as well. De La Rue’s answer to the more exacting requirements of the transit was to design a more accurate scale of equal parts. This was about 15 feet long and was

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constructed out of segments of iron. From experiments with the ‘De La Rue scale’, as it was called at Greenwich, he concluded that there was spherical distortion due to the enlarging lens, but that the scale could be used to map and therefore correct the distortion caused by each instrument’s lens. Newcomb and the American commission, however, did not agree that correcting for lens distortions after the fact was an acceptable solution to the problem. Instead, the Americans decided to avoid an enlarging lens altogether. Based on an instrument designed by Joseph Winlock at the Harvard College Observatory, the American photoheliograph used an extremely long focal length of 40 feet to obtain a 4-inch diameter image without using an intermediary lens. The benefit, as Newcomb argued, was that the enlarged image would then be free of any optical distortion that might be introduced by the enlarging lens. The downside was that, with a body ‘tube’ 40 feet long, the instrument had to run horizontal and would require a very flat and very steady mirror mounted on a heliostat (a mirror mounted on gearwork that followed the progression of the sun throughout the day) to throw the image of the sun into the body. To produce clear undistorted pictures, the mirror had to be ground perfectly flat, and the heliostat had to move without causing any vibration of the mirror. Newcomb published a detailed theory of the instrument in 1872. The paper was worded as an argument in favour of the long-focus method over Britain’s short-focus enlarger method. The problem with using an enlarging lens, according to Newcomb, was not just with optical distortion but also with chromatic aberration, the refraction of rays from different parts of the spectrum to different degrees. ‘It will be entirely inadmissible on this system to trust to any determination of the angular value of a give measure on the negative, because this value will, in the case of an enlarged picture, depend on the refrangability of the light which forms the image.’ The image of an object, when passed through the intermediary lens, will be slightly dispersed, forming a correspondingly enlarged impression on the film. The problem of chromatic aberration was generally considered to have been corrected with achromatic lenses by the nineteenth century. But, according to Newcomb, the amount of residual aberration was too much for the delicacy of measurement required in this case. ‘It is true’, he continued, that if we had a perfectly achromatic combination which would refract all the rays geometrically to the same point, this difficulty would be entirely avoided. But it is very well known that no such combination is possible, and the outstanding uncertainty in the best possible combination will, I conceive, exceed the uncertainty in the present adopted values of the solar parallax.38

Neither Airy nor De La Rue made a direct response to this criticism. On some occasions, Airy forwarded to De La Rue papers containing criticisms of the British method. Invariably, De La Rue’s responses addressed optical distortion rather

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than chromatic aberration. The ‘De La Rue scale’ was designed to take care of optical distortion, and he would refer to these in defence. He also retorted by noting the potentially fatal drawbacks to the long-focus method, especially the feasibility of producing a sufficiently flat mirror and a vibration-free motor. In reply to a letter from a United States Admiral that Airy had forwarded him in May of 1872, De La Rue said that producing the mirror for the long-focus method ‘will present a great difficulty’, and claimed that his instrument-maker, Dallmeyer, had told him that one of the mirrors made by Steinheil for an astronomer in Vienna was ‘useless’.39 Dallmeyer himself, however, was in the process of constructing a long-focus photoheliograph for Lord Lindsay’s expedition (see next section). In short, the situation was this: one method produced known but probably measurable distortions, the other produced no known distortions but might cause ones that would be unmeasurable. It was a lesser-of-two-evils scenario. The debate would not be resolved for another decade, until after the photographic data had been analysed. In the end, Britain, Germany and Russia all decided to use used an enlarging lens while America, France and Lindsay’s expedition chose the long-focus method. Problem III: ‘Photographic Irradiation’ In some over-exposed photographs of solar eclipses, it had been observed that the limb of the moon was ‘eaten-into’ by the brightness of the sun. It seemed that, just as brighter objects may look larger to the naked eye, they might also appear larger in photographs. If this was true it could have important consequences for the transit of Venus photographs. A study of this phenomenon was conducted by Lord Lindsay as part of his transit preparations. He described this spreading-light effect in photographs in the following terms: In all over-exposed photographs of luminous objects upon a dark background, the brighter parts of the picture are found to be surrounded by a nebulous haze or border of light, which increases the diameter of the image formed by the luminous objects at the expense of those which are less luminous. This nebulous haze has often been spoken of as the ‘extension of the chemical action’, but without begging the question of its cause, we propose to speak of it as photographic irradiation.40

Irradiation as it occurred visually or through a telescope was an important, but poorly understood, phenomenon relating to the way light spread or scattered as it travelled through atmospheres and optics. With photography, there were more media to consider; light passed through not only the atmosphere and possibly lenses but also the emulsion that the photosensitive chemicals were suspended in, and there also might be reflection of the light from the backing of the plate into the photosensitive emulsion. There were also the chemical ‘actions’ to consider.

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Did photochemical reactions spread like light through atmosphere? Generally speaking, the longer the exposure the greater the effect of irradiation, but, specifically speaking, the effect varied depending upon the chemicals involved, the light source, the development process, even possibly the temperature. This thing which Lindsay called photographic irradiation was an obscure effect, but understanding it was crucial to astronomical photography, especially if photographs were to be used for precision measurement. Lindsay’s experiments on photographic irradiation in 1872 were designed to locate its problems. Did light spread in the glass negatives, being bounced from the back of the plates? Was it due to the photosensitive material itself, the photochemical reactions somehow spreading beyond the area that was exposed to light? Or was it caused by the enlarging lens, which scattered the incoming light? In these experiments, Lindsay photographed brightly glowing objects under different circumstances. He found that some of the light spreading was indeed caused by light bouncing from the back of the plate. The weaker ‘haze’ of light around bright objects would nearly disappear if the plates were backed with wetted black paper to absorb the light. But there still remained a subtle form of the irradiation, which caused a small but intense increase in the size of a bright object’s photographic image. To test the theory that irradiation was a spread of the chemical activity, he pasted black paper over half of a plate and exposed a bright object at the center of the plate. If the activity spread, it should appear as if part of the image leaked behind the black paper. But the results showed a distinct, sharp line cutting off the exposure where the paper blocked the light. That left the lens, which Lindsay tested by employing circular stops that blocked its outer edges. With stops in place, the remaining irradiation – the increased size of the object’s image – was ‘greatly decreased’. Based on this result, Lindsay made some recommendations for the transit photography: It seems, therefore, fair to argue that the aberration of oblique pencils exceeds in magnitude the other disturbing causes, and that it will be well, in making preparations for the photographic observations of the transit of Venus, to avoid as much as possible all oblique pencils. We would, therefore, place our photographic plates in the primary focus, and thus avoid the necessarily deep curves of any arrangement of lenses which may be used for enlarging the image.41

Not surprisingly, Lindsay and Gill had chosen to use the American long-focus method at their transit station on Mauritius. They concluded that the enlarging lenses of photographic telescopes essentially produced a distortion of bright objects. ‘Oblique pencils’ of light are the rays entering the outer edge of the lens, which thus are refracted at a wider angle than those rays entering closer to the centre of the lens. The real problem was the ‘aberration’ of these rays, the refraction of the outlying, or oblique, rays at such a wide angle that the shape of the

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resulting photographic image was distorted. If one removed the enlarging lens, according to Lindsay, the effect of photographic irradiation is also removed. Problem IV: Choosing the Photosensitive Material One major potential obstacle to success lay in the chemistry of photography. Here again, the national programmes took different paths. In Britain, the lead was taken by William de Wivelslie Abney, a chemist and photographer for the Royal Engineers. The Royal Engineers had been amassing photographic skill and technology for the past decade and was just beginning to document military campaigns photographically. The recent Abyssinia campaign in 1867–9 was one of the first conflicts to be photographically recorded and presented in the press. Similarly in America, the Civil War was the first conflict to be extensively photographed by army field photographers. In Britain, Abney was a central figure in the sphere of military photography. Historian James Ryan has described how it was ‘largely through the efforts of men such as Abney, [that] the RE quickly adapted photography to various tasks in their civil and military duties’.42 When the Chatham School of Engineering created a separate department for chemistry and physics in 1874, Abney would became its first director.43 After the transit of Venus Abney would continue with private research into astronomical photography for many years, working primarily on the photography of the far-infrared spectrum. He lectured often and wrote a popular manual for photography that was reprinted into the 1890s. Airy put Abney in charge of training the transit of Venus photographic staff, which Abney conducted at the School of Photography in Chatham Naval Yard. At Chatham in the early 1870s, Abney developed and tested a new photochemical process specifically for the transit of Venus. The process is described in the first edition of his photographer’s manual, published in 1878, under the heading of ‘collodio-albumen process’.44 The advantage of Abney’s process was that the plates were ‘semi-dry’ (he called it a ‘dry-plate’ process), that is, they could be prepared beforehand and stored for weeks. But his was not the same process as the dry plates that would soon become popular. The ingredients for his process called for, among other things, fresh egg whites, ‘ordinary bitter’, and cotton dissolved in ether (collodion). Abney’s photographic manual gives an idea of the difficulty facing precisionmeasurement photography in the wet-plate era. This is made clear in his detailed step-by-step explanation of the huge variety of processes used by photographers at the time. Aside from the ‘collodio-albumen process’, the book contains eighteen other recipes for photographic emulsions, including a ‘coffee process’, a ‘tea process’ and a ‘uranium process’. There are nearly as many options for how to prepare the paper or the glass plates, which generally involved applying the chosen

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emulsion, brushing it with French chalk, rouge or some other powder, adding a substratum of gelatin, albumen or a solution of india-rubber and chloroform, and finally washing the medium with a preservative, such as beer, pyrogallic acid, tannin, sugar or gum. The process of developing the exposed film was likewise a matter of choosing one’s own recipe from the vast array of materials and processes commonly in use. For those who sought photography so true-to-nature that precise measurements of a photograph could substitute for precise measurements in nature, here is where some of the most difficult problems arose: with every variation in the chemical constitution of the photosensitive emulsion, or the plate preparation procedure, or the development, the reaction of the photograph to light might be different. Some emulsions were not just more sensitive to light than others, but also were more sensitive to certain colours than others. The substratum and developer would also affect the colour and other qualities of the resulting negative – partly for this reason, in precision astronomical photography measurements would typically be made directly from the negatives. Perhaps most worrying was the possibility that, as a wet exposed plate dried, the emulsion would shrink or warp or become distorted in some irregular way. The wet emulsion was sensibly thick; the plates were prepared by being dipped in the photosensitive material. The resulting surface was so irregular that when measurements were taken from these photographic plates using a low-power microscope, the measurements had to be made through a glass with the plates face down, otherwise the microscope would have to be continuously refocused. From the beginning, Airy worried about ‘contractions of the sensitive film’.45 De La Rue had done some experiments to test how the drying of the film may have affected his data on the 1860 eclipse. By observing the position of specks on the glass in respect of markings on a photograph while wet, it could be seen whether they retained their relative positions when the collodion had dried. The result, however, proved that there was no appreciable contraction, except in thickness …46

But De La Rue’s conclusion that that the emulsion shrank only in the vertical plane was not entirely accepted. Asaph Hall of the United States Naval Observatory in particular criticized De La Rue’s experimental method. De La Rue brushed the criticisms aside: ‘there may be some “vagueness” in my description of them, but they quite meet the requirements’.47 This claim would later come under intense scrutiny. Clearly, the chemistry of Abney’s new process was as essential a part of the instrumental process and as liable to produce errors or distortions as De La Rue’s photoheliograph. In late 1873 Abney conducted tests of the collodio-albumen process at Greenwich and Chatham.48 William Christie described the results to

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De La Rue: ‘The dry plate process has more than answered all our expectations and so far we have had no failures, the manipulations are very easily learnt and are apparently much more certain than in the case of wet plates’.49 After Airy received similar reports, he authorized a switch to the new process just months before some of the expeditions began to leave. The French avoided the issue of emulsion shrinkage by choosing the daguerreotype method, which uses silver-plated copper plates rather than wet collodion. By 1870 the daguerreotype – originally a French innovation – was no longer very commonly used, and the photographic advisers in Britain and America seem to have had no working experience with this method. Since Bond’s photograph of the moon in 1851, very little astronomical work had employed the daguerreotype. The American, Russian and German programmes used standard varieties of the collodion wet-plate process. For Airy to rely on Abney’s process was as much an expression of faith in the expertise of the Royal Engineers as his reliance on De La Rue showed his preference for the expertise of Britain’s private astronomers over that of the professional astronomers of the United States, Germany, Russia or France with which he was in correspondence.

Programme Design as a National Product Although the German and Russian programmes were interested in photography, both were also looking to a different technology to avoid dealing with contacts: the heliometer. Heliometers are a form of double-image micrometer, designed for very precise measures of the angular distances between objects seen through a telescope.50 Like photography, the heliometer would be used to measure the distance between the centres of Venus and the sun in mid-transit, thus also avoiding contacts. Unlike photography, however, the measurements would be taken directly from the transit. The Germans were planning four stations with heliometers built by the German maker Fraunhofer. The Russians had ordered three heliometers from the Hamburg company A. & G. Repsold. The heliometric method was also chosen by Lindsay and Gill at Dun Echt Observatory. Lindsay outfitted his well-funded private expedition with a Repsold heliometer. Except in Germany, heliometers were relatively rare instruments. There was only one in England; the Radcliffe Observatory in Oxford had been fitted with a Repsold heliometer in 1849 for stellar parallax research. In America, according to Newcomb, ‘the instrument did not exist’.51 Outside of Germany, there was a common perception that, as George Forbes put it in 1874, it was ‘a very troublesome instrument to manipulate’.52 But Lindsay and Gill, regretting that the heliometric method ‘has not found favour in this country’, argued for its superiority over the contact method, and estimated that the probable error of

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a heliometric result would be ‘considerably less than two hundredths of a second’.53 In April 1871, when Airy had been weighing De La Rue’s photographic plan, he had sought advice from the Berlin astronomer Arthur Auwers, who was a leading member of the German transit commission. Airy asked Auwers his opinion of the various transit methods and explained his concern: In endeavoring to judge of the accuracy of different kinds of observation, I incline very strongly in favor of the ancient method of observing by eye the entry upon or departure from the Sun’s limb … Can the distance of the planet from the limb be measured by heliometer or photography with equal accuracy? I doubt it very greatly … The scale of measure may be fallible and accidental errors in photography may be large … But I am not personally a photographer, and I never used the heliometer.54

Though most comfortable with the ‘ancient’ telescopic method, Airy was more open to photography than to the heliometer and he did not take Auwers’s (or Struve’s or Lindsay’s) advice. Airy did, however, break national lines with his enthusiasm for a second photographic method developed in France just before the transit: Pierre Cesar Jules Janssen’s ‘photographic revolver’. This instrument was designed to automatically take a series of photographs in quick succession, capturing about sixty images per minute. Developed specifically for the transit of Venus, the photographic revolver was contentiously excluded from the French programme.55 It was greeted enthusiastically in Britain by Airy and De La Rue (although Tupman, after some experimentation, advised Airy not to bother with it). The revolver photographs were to be used in a different way from the photoheliograph images. Rather than capturing Venus in mid-transit, these were to be taken at the time around contact. One plate per second would be exposed, and it was hoped that either the black drop would be caught on film (and the time thus exactly known) or that the time of contact could be calculated using the time at which the series was taken and measures of how far the planet moved during the minute. Thus the important information retained in the photographs was the speed of the transit, and without the need for the photographs to be exactly true-to-nature, the revolver method potentially avoided many of photography’s pitfalls. In the final months of the preparations at Greenwich, Airy ordered five revolvers to be made and sent out on the expeditions. To summarize the international picture, there was almost no agreement among the national enterprises over how to proceed with photography in the transit of Venus. Prominent among the differences in instrumentation was the mode of enlarging the solar image. France, the United States and Lindsay chose the long-focus method, while Britain, Germany and Russia chose the shortfocus method. Three kinds of photographic processes were used: the United States, Germany and Russia employed the wet-plate collodion process, Britain

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relied on Abney’s ‘dry plate’ version of the collodion process and France revived the daguerreotype. With only two exceptions, the choices made by each national programme followed national lines – they chose instruments that were conceived of and designed by a countryman (the long-focus method was proposed independently in France by the engineer A. Laussedat), and the instruments were constructed by local makers (in America, the fact that all instruments were provided by local firms such as Alvin Clark & Sons and Stackpole was clearly a source of pride). Airy, for example, relied on the advice of De La Rue rather than any of the French or American photographic astronomers with whom he regularly corresponded (e.g. Newcomb, Hervé Faye, Rutherfurd and Winlock). The first exception is Airy’s enthusiasm for Janssen’s photographic revolver. The second exception is Lindsay’s private expedition, which did not adhere to British makers or place special emphasis on the opinions of British astronomers. Taking positions opposing those of Greenwich, Lindsay chose to employ a heliometer and a long-focus photographic telescope. The contrast between the choices made by Lindsay and Airy may be taken as further support for the idea that at Greenwich Airy was bound – either by his own attitudes or, possibly, by those of the government – to pursue British expertise over international opinion. Do Lindsay’s choices reflect a freedom from nationalistic attitudes that shaped the decisions made at Greenwich? That may be putting it too strongly; ‘nationalistic’ does not properly describe Airy’s inward-looking set of decisions. It is important to recognize the differences between the more banal nationalism of the international expositions (or of the representations of the transit of Venus in the press) and the forces at work here. For one thing, they did not depend upon each other – it is entirely plausible that Airy’s choices would have been the same even if there had been no political or public sense of the ‘scientific credit’ of the country hanging on the transit enterprise. Second, in the case of the forces that made each programme into a ‘national’ one at the level of technical design choices, it seems to come down to issues of trust and associate networks (of instrument-makers and acquaintances with the requisite experience) rather than ideology. In fact, given the time pressure, it would have been hard for the large programmes not to go local. Lindsay showed it was possible, but Lindsay only had to order one photographic telescope, not five. What can be said without hesitation is that the technological design of each programme was a national product. That in itself is not surprising. What is more interesting is how, in this case, because of the strange set up in which so many countries were participating, it becomes so obvious just how much the initial conditions of location and management personnel can affect the ultimate outcome of a programme’s design. That pattern, as we will see, extends well beyond the photographic arm of the programme.

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The Telescopic Plan: Modelling the Transit of Venus In March 1873, De La Rue wrote to Airy about making ‘some experiments to imitate the appearance of Venus on the sun’s disc, that is, to make photographs of the Sun with an Artificial Venus interposed’.56 Airy replied that De La Rue was not alone in starting to think about simulating the transit of Venus; the Russians and the Germans had already created a ‘working model’, and Greenwich was in the process of having one constructed.57 The idea of creating an artificial transit came from all sides almost at once. By the end of 1873 all countries involved would have constructed their own artificial transits. This new interest in modelling for the purpose of training and research – in contrast to the demonstrative and mathematical modelling functions of orreries, planetaria and even astrolabes – is unusual in the history of astronomy, and indeed in the history of science before the twentieth century. Photography was a technological innovation, modelling was a new methodology, something distinct from both observation and experimentation. The subject of models in science today has received much attention from philosophers of science,58 but the history of modelling in science – especially before the computer – is relatively unexplored, making it difficult to make sense of the apparently sudden appearance of modelling in the transit programmes. It was not a matter of technological development; similar instruments could have been produced in the eighteenth century. In fact, in the 1760s, a transit of Venus model had been proposed to the Royal Society, but apparently it was never constructed. Instead, the most famous transit of Venus simulation of that time – a blend of scene painting and orrery-like celestial models – was created by Benjamin Martin for use in his lectures and public shows.59 Cyclones, tidal vortices, the economy and clouds were also modelled mechanically for the first time in the late nineteenth century. From a historical perspective, the development of the model approach may fit an interesting broad-based trend evident throughout Victorian science, and this is an area that deserves more attention than has so far been given by the few studies that have been made. One of these studies deals with Norman Lockyer’s laboratory research on the solar spectrum, which was also a first in terms of laboratorybased attempts to artificially represent aspects of the sun. The conclusion of this study was that the experimental techniques of astrophysicists such as Lockyer generated intense debate within the astronomical community over the utility and scope of inferences drawn from laboratory constructions of astronomical phenomena.60 Interestingly, in the case of the artificial transits of Venus, the applicability of inferences drawn from the models (prior to the 1874 transit of Venus) appears to have been universally and unrestrictedly accepted without

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debate. The origin of this turn towards modelling in the late nineteenth century, however, remains unexplored. To some contemporary journalists, the idea of astronomical modelling was obviously inspired by military strategy. In an article devoted to the ‘Sham Transit of Venus’ in the London Graphic, the author explained that ‘the Astronomer Royal, acting on the principle which induces naval and military commanders to organize sham fights as a preparation for real battle, constructed an artificial model of Venus’.61 This may indeed have been how Captain Tupman of the Royal Marine Artillery, who was in charge of the model experiment and training, thought of the value of simulations. In a rare but important moment of international technical cooperation, the design of the British model was imported from the Imperial Observatory of Russia at Pulkovo. In the summer of 1872, Auwers had written to Airy with results of model training experiments and a technical description of the Pulkovo instrument.62 A first version of the model at Greenwich was erected in October 1873. The event was publicized by a stack of penny postcards sent out with an invitation to view the model ‘exhibiting the phænomena in their true angular magnitude and velocity’.63 Viewing was open to anyone ‘on any weekday before 2 o’clock’, and a partial list of interested visitors includes not only professional and private astronomers but also statesmen, admirals, civil servants and other scientists. The working of the model is clear from Figures 6 and 7. Venus is represented by a blackened metal disk, which is attached to a sliding bar below.

Figure 6. ‘Transit of Venus – Model used for Practice at Greenwich Observatory. Invented by Sir G. B. Airey [sic], Astronomer Royal’, The Graphic, 17 December 1874.

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Figure 7. One of the five training models constructed for each station, here set up at Honolulu. Note how sunlight is being shone through the box from the swivel mirror at the back, creating a sun-like backdrop for the black metal Venus. Reproduced by permission of Cambridge University Library, shelfmark CUL RGO/6-276 no. 37.

This bar is attached to a clockwork mechanism, which pulls it past the triangular opening in the frame. The metal Venus advances very slowly across the opening, less than 1/1000 of an inch per second, at the same speed that was calculated for the transit of Venus. The opening represents the sun, with the two legs of the triangle representing the portions of the sun’s edge across which the planet passes. Natural light was reflected through this opening from a swivel-mounted mirror positioned behind the apparatus. The British, Russian and German models were designed to be viewed through a telescope from a distance of 400–500 feet. In contrast, the French and American models were designed to be viewed from more than half a mile away. The longer viewing distance was intended to allow for more pronounced atmospheric effects, which were believed by some to be an important factor in producing the black drop effect.64 This difference could have been crucial and indeed Richard Proctor, who did not try the British model in London but used the American model in Washington, argued that the British model was for this reason misleading. Alternatives and improvements were often suggested. Airy received half a dozen letters suggesting how to, as one put it, ‘further increase, if possible, the resemblance of your experiment to the facts of the case’.65 But, except for some refinements to the original design (most importantly smoothing the edge of the model Venus), the British model stayed the same. Airy would later regret not acting on some of these suggestions, especially those such as C. Orde Browne’s, which suggested ways of modelling a Venusian atmosphere.

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In the autumn of 1873, the models took centre stage in the transit preparations. Here on the lawns below Greenwich, as in Lockyer’s laboratory work on the nature of sunspots and solar energy, terrestrial model experiments were constructed to provide information about an inaccessible object.66 Airy and his staff would thus make a number of important decisions about the programme design based on the appearances of the artificial transit.

Artificial Black Drop Experiments Though it had not been purposely built into it, the model produced a black drop effect. As Airy described it, ‘There is disturbance of the shape, somewhat similar to Captain Cook’s [i.e. Cook’s drawing of his observations] but very much less’.67 This was an important turning point in the programme. The central but heretofore inaccessible black drop effect had become reproducible and thus measurable. In particular, Stone’s analysis of the effect as reported in the 1769 observations was now taken up in experimental form at Greenwich. The model experiments were geared more to understanding the characteristics of the black drop than to unravelling its cause. The first experiments were conducted by George Forbes, a recent graduate of St Catherine’s, Cambridge, and newly appointed professor of natural philosophy at Anderson’s College, Glasgow.68 Forbes was one of only a handful of transit observers who came from universities and observatories rather than the navy. The main purpose of Forbes’s model experiments was to measure the time difference between ‘true geometric contact’ – when the edge of the model Venus touched the edge of the model sun – and when contact appeared to an observer to have occurred.69 Stone had estimated from the 1769 reports that this interval would be about 9 seconds. In the model, it was found to be closer to 3 seconds. Stone had also argued that the black drop occurred at real contact, and that geometric contact came after real contact. This idea was contradicted by the model experiments. Different telescopes, eyepieces, micrometers and dark glasses were tested out. The performance of different telescopes was studied. Further experimentation showed that this interval of time between black drop and true contact varied with the intensity of light.70 The model used reflected natural light to represent the sun, and By using alternately full sunlight and ordinary cloud light, the black ligament may be seen to appear and disappear … with full sunlight the ligament is still visible eight or ten seconds after true contact, but with dull light it disappears at the third second after contact; it is therefore expected that any atmospheric cause which diminishes the Sun’s brightness will affect the formation of the ligament.71

Forbes also speculated about the cause of the black drop. He argued that the gap between Venus and the Sun at 3 seconds (0˝.111) after contact (measur-

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ing ingress in this case) is within ‘the limiting angle of visibility’, and the light coming through that gap is below the threshold of perception. The time it takes Venus to advance enough so that the light between the two limbs becomes visible is, according to Forbes, the fundamental level of uncertainty of the time of internal contacts. Airy did not agree with what he called Forbes’s ‘inference from irradiation’, but he did not offer an alternative, seeming to be generally uninterested in pursuing causes.72 ‘Irradiation’ was generally considered to be the cause of the black drop. In Forbes’s subsequent articles on the transit of Venus in 1874, he described irradiation as ‘that curious phaenomenon in virtue of which a star, or any bright object, appears larger than it really is’. If, for example ‘a thin platinum wire be intensely heated, it seems to a person distant about fifty feet to be as thick as a pencil’.73 Very bright light was needed to produce irradiation, and indeed the brighter the light, the stronger the black drop phenomenon appeared to be. But under dimmer circumstances, Forbes maintained, there is a similar effect due to ‘mental aberration … a perfectly definite phenomena … that is capable of accurate investigation … caused by a spreading of the excitement of the nerves of the retina, which gives rise to the sensation of vision over a sensible space’ (see Figure 8). It is hard to pinpoint what ‘irradiation’ meant at the time. Bradley Schaefer, in his 2000 paper on the cause of the ‘notorious black-drop effect’, aligns nine-

Figure 8. An illustration of the difference between the paths Venus will appear to take across the sun, depending on how far north or south the observer is on Earth. The illustration also depicts the black drop and how it was thought to be caused by irradiation. Irradiation makes bright objects appear larger, so the sun appears larger than it really is (the real edge is indicated by the dotted line) and Venus appears smaller than it really is (again indicated by the dotted line). From The Engineer, 16 January 1874, p. 35.

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teenth-century ‘irradiation’ with the modern concept of ‘normal terrestrial atmospheric smearing’ – the diffusion of light through Earth’s atmosphere – and notes that this correct explanation was first proposed in 1770 by Lalande.74 Other explanations were common, however. Forbes’s reference to physiology is one. Another held it was due to diffraction through the atmosphere of Venus. A third proposed it was due to refraction in telescope optics. The cause of the black drop effect remained vague. The important result, however, was that the phenomenon – in the model – occurred with regularity, and therefore it could be measured.

Training the Observers The typical expedition staff member was a paid volunteer from the navy who had little or no previous experience in astronomy. The subject of attracting expedition staff was a contentious issue between Greenwich and the Admiralty. According to both Tupman and Airy, the incentives for joining up were far too low. ‘The conduct of the government in its relations with the transit of Venus volunteers is, and has been from the first, calculated to drive them all away rather than to encourage them and secure good men’, wrote Tupman.75 He also claimed that the Admiralty sought out young and unqualified officers who were currently on half-pay in order to lower the expense of hiring the observers. After much haggling Airy eventually secured some increases in the salaries, to £1 per day for station chiefs and 10 shillings for the others while in training, plus full officer pay while on the expeditions. The handful of civilian volunteers was treated even worse. They were not allowed to reside in naval housing during the three months of training and, initially at least, they were not going to receive any pay during that time either. But Airy also managed to increase the civilian rate to £300 per year, training time included. In short, there may have been a degree of prestige but little else that attracted transit of Venus staff. The majority were inexperienced, and basic training in astronomy was therefore necessary. Tupman was in charge of this; he developed a detailed set of instructions (‘you may laugh at them’, he told Airy, ‘but some of the men will know little or nothing about optical instruments when they begin’) and spent most of the second part of 1873 on the education of his recruits.76 The majority of the model training simply involved giving the observers a basic familiarity with astronomical instruments and with the specific routine to be followed in the transit of Venus observations. During the two or three months that volunteers were required to spend at Greenwich, each recruit was periodically ranked according to ‘astronomical fitness’ and ‘photographic fitness’. Although there were some who Tupman thought, even after training, would ‘never become good, or reliable observers’ or who made unpardonable

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mistakes (such as one who cleaned the graduated scale of an instrument with abrasive powder, thus blurring the divisions and requiring a new scale to be fitted), men were rarely dismissed. There was always the worry that a replacement would not be found.77 Training covered not just handling instruments but also packing and unpacking the instruments and assembling the prefabricated instrument cabins according to exact instructions. Each station would be equipped with prefabricated observation cabins for the transit instrument, the altazimuth, the equatorial and the photoheliograph. They were either rectangular or hexagonal in shape, with roll-up slate roofs and unfinished clapboard sidings. In a series of practice runs, all forty cabins were erected on the lawns around Greenwich. The structures were to be identical at all stations, inside and out. Within each cabin, every minute detail of the material arrangements had been planned out. The printed layout of forms for recording observations was considered. Their placement about the observer was carefully planned in order to ensure efficient switching from one form to the next. Likewise the optimal placement of accessories such as chronometers, eyepieces and glasses were precisely determined, so that they would be comfortably within reach. The aim was total environmental and material uniformity. The thoroughness of this planning was both a mark of Airy’s micro-managerial style and a consequence of the specific challenge posed by the transit of Venus method. That intense focus on environmental and material uniformity within each hut isolated – but left unresolved – the deeper problem of getting uniformity in the observers’ timing of contact. The core of all this preparation was also the most delicate: training observers to uniformly interpret the moment of contact. Here is where the simulation transit of Venus came to play an absolutely crucial role in the preparations. Practice sessions for contact timing began just after the model was completed, in November of 1873. The goal was to minimize any differences in interpreting the appearances at contact across observers. This involved, most importantly, learning to discern particular phases of the artificial black drop through a specific set of exercises. Airy dictated instructions for how the contact training was to proceed: Let all the observers by turns observe the Working Model with all these instruments; and, when they are familiar with appearances, let them practice the [no]ting of times. The signals will usually be related to the formation of the drop and the formation of the clear circle.78

Observers measured the model black drop again and again, with different telescopes and eyepieces giving different appearances to the drop, marking the times of contact on special worksheets. There was a special focus on using eyepiece

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micrometers to measure the closing ‘cusps’ – the edges where the sun’s limb was broken by the silhouette of Venus – as the moment of contact neared. Observers were not being trained to measure ‘geometric contact’ (when the edge of the metal Venus coincided with the edge of the artificial sun) but rather the moments in which the model black drop formed and then broke. As observers gained more experience in observing the formation and break of the drop, the disparity between different observers’ timings decreased. This proved to Tupman and Airy that the model was a success. The benefits of observers ‘becoming familiar’ were significant and measurable: From the observations with the Model Transit of Venus made at Greenwich, the following facts appear. One. It requires considerable experience for an observer to appreciate all the definite changes of appearance which occur. Two. When two observers describe a particular phase which they see, and determine to observe this phase together, the times recorded by each are generally accordant within a fraction of a second.79

It should be emphasized here that, because of the way in which the parallax was to be computed from the observations made, obtaining correspondence among observers on the timing of an event during contact was the essential thing – it didn’t matter what event was singled out and timed by all the observers, just that everyone singled out the same event. Thus the importance of the fact that observers could ‘determine to observe this phase together’ with the aid of the model. Once its power as a tool for producing consistency in observer judgements was demonstrated, all model activity was stepped up. On Forbes’s suggestion, four more models were made in London to be sent out with the expeditions.80 In India and Australia, versions of the same design were locally produced. Before heading off to Mauritius, David Gill, the head of Lindsay’s expedition, visited Greenwich in order to observe Airy’s ‘beautiful Model Transit of Venus, so that we may agree in observing precisely the same phenomena’.81

Model Training versus Personal Equation Measures The model training plan has some connection to Karl Friedrich Wilhelm Bessel’s concept of ‘personality’ or ‘personal equation’ developed in the early nineteenth century (mentioned in the Introduction to this volume). Through analyses of large sets of observer data, Bessel discovered that individuals display small but constant differences in recording the time a star passes the telescope’s crosshairs. In order to remove the differences, a value was assigned to each observer that would, in effect, calibrate their observations against a ‘standard observer’, who had been chosen for falling in the mean. So, someone designated a ‘fast’ observer relative to the standard would have a fraction of a second subtracted from his

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stellar transit times, while a ‘slow’ observer would have a similar amount added to his times. The personal equation was thus defined as a statistical bias in measurement caused by the observer himself that must be eliminated from final results. The personal equation was developed to uncover discrepancies across observers in stellar wire-transit recordings. These discrepancies appeared as very small differences in the way observers performed a very simple, specific task. Transit of Venus observations and the black drop problem, however, brought new challenges to the issue of observer subjectivity. The discrepancy across observers was much greater, the phenomena of the transit were much more complex, and the goal was not just to uncover and account for discrepancies but to remove them altogether. Some historians have read the rise of the personal equation as a significant sign of the concomitant rise of the ‘factory mentality’ of the state observatories.82 Schaffer in particular has made an association between craftsmen’s loss of skill in a factory setting due to division of labour and observers’ loss of authority within the observatory due to the rise of ‘surrogate’ observing technologies such as the personal equation and chronographs. The rise of the personal equation, according to Schaffer, involved ‘a loss of the observer’s authority within the discipline of astronomy. That loss was of immense importance for astronomers’ styles of work and for their public image.’83 In the case of the transit of Venus, the situation would in fact be the opposite. Only observers who had received training on how to observe the black drop were deemed to have the authority to make useful observations. While the training aimed to remove personal differences and make the observers, like menial labourers, interchangeable, the training also bestowed on the observers a particular and valued skill. Furthermore, while Airy has often been taken to have been the most ‘factory minded’ of observatory managers, in the case of the transit it also becomes clear that, of the major European observatories, Greenwich had the least previous experience in training observers so thoroughly. In France, for example, a second artificial transit of Venus, designed specifically for black drop experiments and personal equation measures, was developed by C. Wolf and C. André.84 It was a modified version of the electrical ‘artificial transit’ instrument that Wolf had developed as part of his famous investigations of the personal equation in 1866.85 At Greenwich, in contrast, the transit of Venus model was the first mechanical training model ever to have been used, and its design was copied from Germany.86 Contrary to what is sometimes claimed, Airy’s work on finding differences among the Greenwich observers only involved calculating the personal equation from existing tables of observations. It would not be until 1887 – under Christie – that an artificial transit machine similar to Wolf ’s was installed at Greenwich.87 It should be made clear that while personal equations were determined for transit of Venus observers, they were only sought for the auxiliary astronomical

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work, especially the observations required for longitude measures and even for measuring the photographs. Lindsay’s and the British reports discuss determining personal equations for stellar transits and altazimuth measures, as well as – in a new application of the concept – for the production and reception of telegraphic time signals in determining longitude by telegraphy.88 But for the Venus transit observations no significant effect of personal equation had been found during the preparations at Greenwich.89 The disparities across observers’ recordings of transit contact times, though at times large, were not considered innate and were not as regular as was the case with the ‘personality’ differences. Hence the level of training that transit observers underwent for observing the black drop went well beyond any training or measurement that had been pursued in connection with the personal equation. In contrast to the personal equation measures, the goal here was not to measure but to eliminate disparities across observers. Furthermore, these disparities were not considered to be physiological or innate (as with the differences in observer ‘personality’) but linguistic or intellectual and therefore capable of being modified through experience. In this way, model training in the transit of Venus preparations represents a pursuit of observer uniformity on an entirely new level. It was an impersonality achieved through training, a trustworthiness gained from demonstrating skill.90 The hope was that the transit observers, many of whom had started out as complete astronomical novices, would leave Greenwich for their stations as expert observers and recorders of the phenomena of contact.

The International Melee ‘A large majority will agree’, wrote Simon Newcomb in an 1872 report, that ‘[the telescopic method] cannot be safely depended upon until some method is found to guard against the errors to which experience shows it to be subject’.91 In fact the commissions and managers of the national transit of Venus programmes could not even agree on this. According to Newcomb, the results from the observations of the transit of Mercury in 1868 showed that modern telescopic equipment and observational methodology was not enough to solve the black drop issue. He and the American commission therefore placed most emphasis on the photographic method. Airy, on the other hand, repeatedly expressed his preference for what he called the ‘traditional’ eye-observation method. He was sceptical that photographs could be obtained without distortions or other significant errors in representation. He was also – as was Newcomb – sceptical of the German and Russian plan to make measurements of the transit using heliometers. Here the worry was that, as with any delicate, complex and relatively new instrument, there was a high risk of instrumental error. The only alternative

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method that interested Airy was the Janssen photographic revolver, which neither the French nor any other country took very seriously. During the preparations for the transit of Venus, Airy’s attitude was not ‘wholly international in his approach to science as an enterprise’, as some biographers have suggested was his style.92 Furthermore Greenwich, in this case, did not take on the role of ‘the international observatory’.93 There was in fact no single authority in the international astronomical community to which all countries looked. At the same time, there was a strong international astronomical community. Airy was in close communication with the heads of other programmes, especially Struve at Pulkovo and Auwers in Berlin94 Within that community there simply was no expression of interest in international collaboration on the transit of Venus enterprise. Adding to the divergence of national programmes was the fact that Airy delegated important decisions to private astronomers and military engineers, and these men did not themselves belong to an international community of practicioners. Hence technical skill and knowledge was generally confined by national borders. At the end of the four years of preparation for the expeditions, a range of solutions had emerged. Countries would employ, in various combinations, four different methods of recording data: eye-observations of the time at which the transit began or ended (observations of contact), photographic records of the time at which the transit began or ended (the Janssen revolver), live measurements of the distance between the centre of the sun and the centre of Venus during the transit (the heliometer) and measurements after the fact of the same taken from photographs of the transit of Venus. Each method had its pros and cons. Photography avoided the problems involved in interpreting the moment of contact, but introduced the many uncertainties in how, exactly, a photographic record represented the world. The real benefit lay with the large quantities of data produced by photography. The telescopic plan, on the other hand, had the benefit of using standard, traditional precision instrumentation for which the potential errors were very thoroughly understood. The uncertainties lay in how well the model training had prepared the observers for interpreting contact. All of the solutions had in common the fact that each was subject in its own way to classic problems in precision measurement. Each grappled with unknowns about the object being measured, potential errors of the measuring device, and the fallible judgement or practice of the measurer. The broad international scatter of technical solutions described above is perhaps unusual in that, though there was serious disagreement, the situation cannot be cleaved into any simple controversy-shaped debates between two camps with different needs and interests, such as illustration versus photography or human observation versus photographic record. Opinion and controversy cut in all directions. There were too many sides and too many issues. There were so

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many unknowns – about the phenomenon itself as well as the new technologies of measurement – that, as the expeditions got underway, the question of which method would produce the best result was for all parties involved completely up in the air. By 1874 there were doubters, such as Urbain Le Verrier and the physicists Hippolyte Fizeau and Alfred Cornu in France.95 They were both involved in measuring solar parallax by completely different means. In Britain the most vocal call for an alternative approach came from Charles Piazzi Smyth, the Astronomer Royal of Scotland. Smyth was convinced by the work of archaeologist William Petrie who theorized that the pyramids of Egypt were evidence of advanced natural knowledge. Petrie had argued that the great pyramid had been constructed on a 10:9 ratio (rising 1 cubit for every 10 cubits in length) because it closely embodied the value of pi.96 Smyth discovered that 109 times the height of the great pyramid equalled 91,840,000 miles, which he believed was the true value of the sun’s distance from the earth. The pyramid therefore ‘forms therefore in itself, and in all its grand simplicity and antiquity, a single representation of the whole of the numerous, laborious and most costly sun-distance results of all humankind even in the present age’.97 However, all of the alternatives were momentarily dwarfed – for the five years leading up to the transit – by colossal worldwide interest in the transit of Venus. A bird’s-eye view of the worldwide transit of Venus enterprise in early 1874 would reveal an absolute mishmash of methodologies. A messy tangle of technologies were in play, and yet each observer faced the daunting fact that no one knew what would happen at the moment of contact. At the same time, there was reason to believe that the 1874 observations would provide a greatly improved measure of the sun’s distance. The general assumption was that, compared to the observations of the 1760s, the observers of 1874 had not only more sophisticated telescopes and entirely new technologies of modelling, photography, telegraphy and steam travel, but also a better grasp of the central problems, and more effective ways of finding their solutions. In all, as the expeditions set out in the summer of 1874, confidence was high.

5 THE EXPEDITIONS

We have, first of all, the remarkable spectacle of trained observers of almost all nationalities … distributed among some seventy stations, some of them the most inhospitable islands of the Southern seas, engaged upon one of the most abstract inquiries which can be imagined.1 The Times (London), 9 December 1874 This brought him on to the time of starting with the Transit expedition, when he and his kind became lost to the eye of civilization behind the horizon of the Pacific Ocean. Thomas Hardy, Two on a Tower (1882)2

Figure 9. Expedition members gathered at Greenwich prior to the transit. Reproduced by permission of the Royal Astronomical Society Library / Science and Society Picture Library, shelfmark X101/2154.

The image of over 75 expeditions networking the globe would be an impressive spectacle even today. At the time it was also a very physical expression of Europe’s – and especially Britain’s – global imperial presence. The census of 1871 counted over 234 million people living in the British empire. Of those only about 13 per – 89 –

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cent were in Great Britain and Ireland. The empire’s land claims covered over 7 million square miles. The British Isles and Ireland were about 1 per cent of that total. On 8–9 December, the transit of Venus would be front-page news throughout Europe and America, and to much of the globe where there was a European-language press. In the press coverage, emphasis now shifted from inter-European comparisons (described above) to straightforwardly jingoistic celebrations of the expeditions as part of the imperial fabric of the time. Like the popular genre of serialized travel, such as Thomas Cook’s journals from the first round-the-world tour (1872), and Jules Verne’s fictional journey Around the World in Eighty Days (1872), pictures and stories from the transit of Venus expeditions fed a public appetite in Britain for tales of travel, exoticism and heroic exploration. Yet against the backdrop of a peaking empire, the transit of Venus expeditions were just one fleeting and relatively minor event in a world absolutely defined by colonial action and exploit. The amount of material in the press, journals and personal accounts that remains from these 75 expeditions could be the subject of an entirely separate book. If such a book were written, the challenge would be to find the overarching theme or material that unites the exponential number of cultural encounters. What draws together the stories of Japan welcoming Mexican astronomers, the American experience in rural Tasmania, the Germans in Persia, the British in Cairo? Of course what gives some unity and distinctiveness to the various expedition histories is their status as scientific endeavours. But even the significance of that status varies greatly from place to place. Focusing on the British perspective, it will come as no surprise that personal accounts and newspaper pieces were suffused with a certain cultural arrogance. Indeed these expeditions were just the kind of exercise that underpinned that jingoistic attitude that is so characteristic of late nineteenth-century Britain. Science played an important role in justifying the colonial enterprise. Historians have examined how, as the nineteenth century progressed, the British Empire’s ‘civilizing’ mission increasingly included the spread of science.3 In colonial India, for example, studies have examined the expression and impact of the ideology of science as a civilizing force. One colonial administrator expressed an imperial conception of astronomy in particular in the following terms: In prosecuting the study and in contemplating the structure of the universe … [natives] can scarcely fail of relieving themselves from a load of prejudices and superstition; they will thus gradually, in proportion as their knowledge is spread, become better men and better subjects, and less likely ever to be made the tools of any ambitious man or fanatic.4

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Often Christianity was key to justifying the civilizing mission, but science and technology could play that role just as well. There was often an emphasis on the idea that science was both a sign of civil society and a means of its dissemination. This is an established theme in studies of science and empire, and one which finds expression in the transit of Venus enterprise as a whole. But, once again, the sheer geographical diversity of the enterprise makes it impossible to give any single description of their significance even from the British colonial perspective. One example that complicates the picture is Piazzi Smyth’s devotion to the theory that the great pyramid of Egypt encoded the true value of solar parallax, discussed in Chapter 4. Another press perspective saw the transit as not only further justification for British imperialism but as an ideal form of cultural expression. In the satirical pages of Punch, the enlightened transit of Venus expeditions – with their noble scientific aims – cast a shadow on the rest of the colonial exercise: … They went forth in peaceful battalions, The secrets of Science to clutch, Americans, Germans, Italians, With Frenchmen and English and Dutch; … When, braving sub-tropic malaria, And noses and fingers that freeze, From Kerguelen to dismal Siberia Astronomers sail o’er the seas, Fair Venus, our beautiful neighbour, Throws down her distinguishing light, ’Twixt the armies for Science who labour, And the armies for conquest who fight. Punch with patience waits tidings of Science, But waits, with a thirsty impatience, For the time when all warlike defiance Will cease among civilised nations. From quarrelling canst thou not screen us, O brightest and clearest of stars, And let the last Transit of Venus Be crowned by the Exit of Mars?5

Along similar lines, one aspect of the transit of Venus that gave it a very unique place within British colonial ideology is that (as has already been discussed), by the late nineteenth century, transit of Venus expeditions already had an important place within the common Whiggish interpretation of the history of British imperialism. Transits of Venus were at the very roots of the colonial histories of Australasia and Polynesia, all of which were explored (and in some cases laid

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claim to) on Cook’s 1769 expedition. In the independent kingdom of Hawaii, the long story of the developing relationship between Europeans and Hawaiians is strangely tied to the cycles of the celestial event. The visiting British astronomers were seen as the latest chapter of that story. For the colonial governments in New Zealand and Australia, the transit of 1874 was a time to reflect on the role of scientific enquiry in the history of their nations. In the town of Lyttleton, a banquet was thrown to honour the British expedition to New Zealand. Addressing the banquet, the president of the Philosophical Institute argued that the post-Cook era of colonization: shows the influence of science in promoting the civilization of mankind and material progress of the world. Without [Cook’s] voyage, undertaken in the interest of pure science, this portion of the Southern hemisphere would not, in all probability have been as it is now, an important portion of the British Empire, with so many of the comforts and enjoyments of European life, and the high aims and aspirations of a steadily-advancing community.6

Here is historical mythmaking in action. Nineteenth-century renditions of Cook’s voyage typically claimed it was ‘in the interest of pure science’, not, as it is now understood, in the interest of geographical exploration for the purpose of colonial expansion. At the Otago Institute’s annual address, the president described the country’s own aspirations to join in the European transit venture: ‘[In the next transit of Venus] New Zealand will be able to produce its own astronomers out of its universities and … the government will be strong and wealthy enough to make use of the local talent and make its own expeditions and deductions.’7 In New Zealand, as in other young or newly unified countries, such as Mexico and Italy, to launch a transit of Venus expedition was seen as a mark of cultural distinction. Of course, the transit of Venus also took on entirely different meanings for the non-European communities in the parts of the world where it was visible or where expeditions were sent. The vast majority of those perspectives have not been preserved or uncovered. But one that does survive is in writing of C. Ragoonatha Chary (1828–80), the first assistant of the Madras Observatory. In his 1874 booklet The Transit of Venus, Chary introduced the problem of the sun’s distance, and gave some details of the coming European expeditions. Chary’s intended audience was Indian, and the booklet was published in English, Sanskrit, Canarese, Malayalum and Maharathi. Structured as a dialogue between student and teacher, it gives a thorough introduction to the subject of Venus transits, and, along the way, offers reflections on European culture and science: Pan. … You say … that Europeans were making grand preparations to observe the approaching Transit of Venus. Is it simply for the sake of curiosity that they put themselves to so much trouble and expense?

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Sid. Europeans generally put their money to very good use. You must not suppose that the practical people, who have constructed so many thousands of miles of Railway, and who have almost annihilated distance by means of the Electric Telegraph, will spend millions of rupees merely to satisfy their curiosity. They expect much practical good to result from the observations of the approaching transits as they furnish the best means we have of accurately determining the parallax of the Sun, and hence the distances and dimensions of the Sun and the planets. … Pan. Ah, Sidhanti! Some ignorant men among us despise the European and call him a heenah, but after what I have heard from you I cannot help having the greatest respect for his industry, intelligence, and laudable attempts to extend human knowledge … … Sid. [after describing the instruments and plans for the stations] In short, nothing will be neglected that is worth observing, but every phenomenon that can present itself, whether foreseen or otherwise during the transit, will be most scrupulously recorded. Pan. It is no wonder that the people of Europe are so much in advance, seeing how persevering they are, and how many public-spirited men there are among them. What Hindu gentleman of the present day evinces the same interest in science that the European does? Are there men among us who will devote their whole life and fortune to advance human knowledge? Unfortunately the answer is, that there are few such men.8

Chary used the transit of Venus enterprise here to make an argument that a society which pursues science along European lines is also a healthy and respectable society. In other works Chary aimed to preserve and develop India’s own astronomical heritage. Although he frequently contrasted the predictive powers of Western astronomy – particularly evident in the precise timing of the coming transit of Venus – with that of the Sidhantis or Hindu astronomers – who ‘cannot predict it with even a rough approach to accuracy’ – he presented Indian astronomy as having only very recently fallen in decline as a result of political instability.9 In an address to a newly-formed scientific society in Madras, Chary proposed to write an astronomy textbook for Indians that would not only revive the history of Indian astronomy but also generate interest in the western forms of the subject as well.10 Even in the transit booklet Chary balanced Indian and western astronomical practice, as in the conclusion: Pan. My sincere thanks are due to you for the explanation of this phenomenon. I have to search the Shastras to find out if any ceremonies are prescribed to be performed on the occasion; and what is more important to me, I have to provide myself with a telescope to observe this most interesting sight.11

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Chary promoted a certain version of European scientific superiority from within the Indian community. But the historical context of Indian astronomical practice informed in very specific ways how European astronomical activity was viewed. As it turned out, Chary himself would not play a part in the official British expeditions. His supervisor at the Madras Observatory, Norman Pogson, lacking the public-spirited interest in the transit expeditions of Chary’s Pandit, had asked Airy to be left out of the transit preparations. Consequently, the Indian station – an important addition to the photographic plan – would be operated by J. F. Tennant out of Calcutta.12 In this chapter, the expeditions will be explored from the perspective given by the letters and reports of the expedition members. The station at Cairo is taken as a case study, but material is also drawn from the other British expeditions.13 Browne’s lengthy letters to Airy make it possible to follow not only the social and political dynamic of the camp as it was established in the Cairo area, but also some details of the work routines at the station. So, as we turn to the expeditions themselves, the focus shifts from the special preparations for observing the transit of Venus to the auxiliary work of finding latitude and longitude. Here too, the transit became an occasion to experiment with new methods and to refine the capabilities of old ones. And finally, at the centre of the entire enterprise, are the few hours of the transit of Venus on 8–9 December. In the penultimate section of this chapter, the book reaches the celestial climax on which this entire story turns. The chapter concludes by returning to the wider perspective, sampling from the press coverage around the world on the day of the transit. In some ways this is also where, on the public stage, the expression of the ideological significance of the transit enterprise would reach its climax.

Establishing the Observation Stations: The Case of Cairo A recent history of Victorian eclipse expeditions concluded with the observation that, while the participants often invoked the tradition of James Cook, the Victorian expeditions in fact had more in common with Thomas Cook’s tours than Captain Cook’s voyages.14 Recent growth in communications and the culture of travel shaped both the expeditions and their representations in the press. Eclipse expeditions were relatively frequent, and typically the participants were wealthy private astronomers. As we will see in the case of the expedition to Egypt, however, the transit staff were received as official envoys of the state, and were often given material support by local governments. During the three months that C. Orde Browne was stationed in the Cairo area, he regularly sent letters to Airy, describing not only the astronomical work, but life in the city and the social scene at the camp. The letters begin in Alexandria, where he and his wife disembarked from the Hindoostan on 8 Octo-

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Figure 10. ‘Plan of the Environs of Cairo showing the position of Captain Orde Browne’s Encampment on Jebel Jeushi, Mokattam Range.’ From G. B. Airy (ed.), Account of Observations of the Transit of Venus, 1874, December 8, Made under the Authority of the British Government, and of the Reduction of the Observations (London: Her Majesty’s Stationery Office, 1881), plate 8. Reproduced by permission of the Bodleian Library, University of Oxford.

ber. From his base at the Hotel de l’Europe, he met first with General Stanton, the British Consul-General in Egypt, who, as Browne had hoped, was able to prevent the customs officers from opening and inspecting the many tonnes of instrument cases. Stanton also had some important weather updates for Browne. Heavy mists had lately been hanging over the city in the early morning, and since egress would occur just over an hour after sunrise, this was a serious concern. Browne’s original idea had been to set up the primary station in the Citadel, a fortress at the centre of the city. But Stanton suggested that, in order to avoid the mists, Browne established camp in the Mokattam Hills, a desert mountain range just behind the city to the east (see Figure 10). Within a few days, Browne and his wife had moved on to Cairo. The first week was spent in a marathon of diplomacy and social networking that began, most importantly, with a visit to the Khedive, Isma’il Pasha. The Khedive was ‘gracious’ and ‘polite’, generously offering Browne many forms of assistance: tents, guards, officers, use of railways and steamers, and an extension of the telegraphic line up to the station. Browne was then left to seek out those who could make good on the Khedive’s promises: the Minister of Foreign Affairs, the Minister of War, the Minister of Justice, the General of the Railway, the Superintendent of the Telegraph, the Chief of Staff and an expatriate engineer who would help Browne with the logistics of engaging ‘men and beasts and carts to

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get the things up to Mt. Mokattam’. ‘You may see how one has to assert oneself sometimes, owing to the routine and complication of arrangements here … having spontaneously been offered a guard I had to make I think seven official calls to get it posted.’15 Ten days and many more meetings later, the movements to camp began. From Cairo, William de Wivelslie Abney and his crew set off on a Khedive-supplied steamer, supposedly the fastest of the Egyptian fleet, to Thebes, where he would set up the auxiliary Egyptian station.16 As for the site in the Mokattam Hills, a rail line had been extended – specifically for the transit party – to the base of the hills; but, from there, a steep and rocky footpath was all that led up to the chosen site. Royal mule carts and labourers brought up the supplies and instrument boxes, which were marked with a red star if they contained something delicate so that the multilingual crew knew to treat it with care. Browne described with awe the physical challenge of establishing camp. So did a correspondent for the Daily News who had been dispatched to cover the transit expedition for the paper. The correspondent described the scene thus:

Figure 11. Front embossing for the hardback binding of the year 1874 for Illustrated London News. The image shows Venus in transit, and, below, Browne and a bowed, barefoot Egyptian labourer surrounded by crates labelled ‘Transit of Venus’. Reproduced by permission of the Bodleian Library, University of Oxford.

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Figure 12. ‘Landing stores on the beach – Rodriguez.’ From Illustrated London News, 28 November 1874, p. 517. This photograph was taken using the photoheliograph. The rectangular box being levered by dozens of locals contains the transit stones, which are heavy pillars that secure the position of the instrument used for longitude observations. Reproduced by permission of Cambridge University Library, shelfmark CUL RGO/6-276 no. 47.

It is perfectly astonishing what weights the Arabs can carry. One box which, I am informed took six men to carry in England, was shouldered, or rather ‘backed’ by one of these natives for a distance of 60 or 70 yards … There is a delightful division of labour, though, in this mode of transit, one man bears the load, and perhaps six others surround him, and do the groaning for him at each step he takes. A constant reference to Allah by the chorus appears to have a marvellous effect in lightening a load.17

The scene was also depicted in the Illustrated London News. A version of this image, reduced to a compact icon of imperial dominance, would be chosen to decorate the paper’s binding for the year 1874 (see Figure 11). Photography and the cheap periodicals market together played an important new role in bringing the world, the empire and imperial expeditions of all kinds into the British view.18 The images of the transit in the press were typically based on photographs taken by expedition staff, either with one of the photoheliographs or with travel cameras brought for the purpose of recording. Some of these would make it into the papers (see Figure 12). Abney, who was stationed near the temples and ruins of Thebes, produce an entire album of photographs of the surrounding archaeological sights, which was later commercially sold.19 Along the road leading from the specially-built rail line was a guard of ‘police’ and mounted soldiers, which remained at the camp throughout the expedition. The four instrument huts from Greenwich – for the transit instrument, the altazimuth, the equatorial and the photoheliograph – were easily assembled, though the slate rooftops chattered loudly in the strong winds.20 Installing the

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instruments was much more difficult. To set a sturdy foundation for the transit, transit clock, altazimuth and photoheliograph, the hard rock of the hills had to be cut into and cement foundations lain with water carted up from the city. Lastly, at the Khedive’s substantial expense, a telegraph line was extended from the centre of Cairo all the way up to the camp. Once established, the camp was a well-equipped, comfortable and self-consciously civilized establishment. The tents provided by the Khedive, over a dozen in all, were ‘magnificent’, ‘incomparable’ to the British supply standard issue. As for furniture, Mrs Browne had bought chairs, tables and rugs in the city, all of which was later to be resold. Plenty of ‘pipes and coffee’ for entertaining had been hauled up to camp as well. Aside from Mrs Browne, two other women had also joined the camp, Emily Newton, sister of the observer Lieutenant Newton, and Miss Adelis, a companion of Mrs Browne. Always concerned to display his financial reasonableness to Airy, Browne made it clear that the women paid for all of their food and drink, and that their ‘keeping house’ saved him ‘much expense and labour’.21 Although initially only travel companions, in the end both Mrs Browne and Emily Newton would make contributions to the astronomical work. The successful establishment of the camp, including such luxuries as a telegraph line and a guard, was largely due to the generosity of the Egyptian government, something that Browne fully appreciated. As a sign of gratitude, Browne, after hearing that the Cairo Observatory was in need of a good astronomical clock, arranged to have the expedition’s transit clock presented to the Khedive as a gift. ‘It cost us about 40 pounds’, he told Airy, ‘but Dent [the maker] would charge him more’.22 This in fact would not go much towards financially reimbursing the Egyptian government –the railway extension to the base of the hills alone cost around £90. The real form of reimbursement was made by opening up the camp for curious visitors and for entertaining. Almost every day Egyptian or foreign dignitaries would visit the camp, where they might observe the model transit of Venus before having a (non-alcoholic, in contrast to the other British stations) drink and a smoke with the visiting astronomers. For the Cairo elite, the transit of 1874 certainly was, to use Alex Pang’s phrase, the social event of the season.23 It was also precisely the right time for the British to benefit from the generosity of the Khedive. Since Isma’il became the Khedive in 1863 he had been spending lavishly and running up debts to around £7 million per year. His spending far exceeded the revenue that was being brought in by the government’s 50 per cent stake in the Suez Canal Company, which had opened in 1869. The Egyptian government, while acting as such a generous host to the British expeditions, was itself in desperate financial circumstances. One year later, in the autumn of 1875, the situation reached breaking point: the Khedive was forced

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to sell all of his shares in the Suez Canal Company. These shares had immense political value because they translated into control over the canal itself and thus one of the most important shipping and trade routes for Europe. The French had established close relations with the Egyptian government in the 1850s and eventually, despite fierce opposition from Britain, provided the support that brought the canal into existence. In 1875, France still had the upper hand in the region. Now, with the Khedive’s stake in the canal up for grabs, Britain had a chance to become a player in the region. A swift private deal struck between the Khedive and General Stanton secured Britain’s hold on the shares. Just eight years later, the British occupation of Egypt would begin.24 In 1874, diplomatic relations between Egypt and Britain – between the Khedive Isma’il and General Stanton – were invaluable to the British Empire. The visiting astronomers were given intimate access to the Khedive’s family. The resulting social and intellectual exchange gave Britain one more link to the Khedive’s inner chambers. This was made possible, in part, by the high regard in which astronomical expeditions were held. Clearly the Khedive, despite financial straits, was motivated to patronize local and British science. Historians have noted that his was a West-looking administration and that he invested in utilitarian projects designed to modernize the region.25 Perhaps the Khedive was seeking closer political ties to the British government. Or perhaps he regarded the visiting expedition as a stimulant for social development and for scientific advancement within his own country. The British expedition does seem to have had some impact on science and technology in Cairo. In particular, the Khedive’s attention was drawn to some of the problems at the Cairo Observatory, and Brown may have inadvertently induced the Cairo railway stations to switch from apparent to mean solar time.26 Certainly, however, Britain got the better end of the bargain. While Britain benefited greatly from the Khedive’s interest in the transit of Venus, in the end the expeditions seem only to have deepened his country’s debt.

Environment, Local Time and Latitude: Work Routines at the Stations In early November, about a month after arriving in Egypt, Browne and his assistant, Lieutenant Newton, were prepared to begin astronomical work. With a month to go before the transit, training on the model continued and the observations for longitude and latitude had begun. For the latter, this meant nights spent observing stellar transits and occultations of stars by the moon, and days spent reducing the previous night’s observations. For the most part this work was the same at all stations; latitudes and local time were found with identical transit instruments and altazimuths, which had been ordered especially for

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the expeditions. The only real variation on the routine was caused by different environmental pressures and disturbances. In Hawaii, there were courtly visits, hands swollen with insect bites and episodes of drunkenness. During a storm, a falling palm tree nearly obliterated the transit hut. One member ‘met his end with the courage of an English gentleman’ when he and George Forbes tried the local sport of surfing.27 In Kerguelen, cloudy weather prolonged the stay, rations began to run out and hunger set in. The ship captain resorted to serving ‘Kerguelen cabbage’, mussels and penguins, reporting to the Admiralty that unfortunately ‘ducks were not as plentiful as reports had led us to expect’.28 In Rodriguez, there were monsoons. And in Egypt, Browne complained about the heavy social obligations: While trying to complete my copy of last night’s reductions I was interrupted by the arrival of Professor Döllen, [a senior astronomer from Pulkovo spelling and head of a Russian station at Aden] and shortly after Hassein Pascha (the Khedive’s third son), the German Consul General, a German count and some others. I mention this to show the trials we have in the way of interruptions … I don’t know what I would do if I had not a long rough mountainside between me & Cairo.29

He also mentioned vultures, hyenas, the occasional scorpion or cobra, high winds that drowned out the sound of the transit clock, and sand scratching and clogging the pivots of the instruments. The potential for such environmental pressures to seriously disrupt the routine of observations should not be underestimated. The work of nineteenthcentury observational astronomy was very delicate physical labour. As the use of the personal equation in data analysis makes so clear, in the abstract the body of the observer was regarded as part of the instrumentation. On the ground as well, observers sought to perform with the impersonality of an instrument. Because, on these expeditions at least, recording the time of the observation was done by watching the approaching stellar transit while keeping time by listening to the tick of the clock, the work required dexterity and coordination. Browne, for example, described how, after one hyena visit to the camp, it took Newton half an hour to calm himself at the telescope before he was ready to continue observations.30 For at least a month, nights and days were devoted to locating the station as accurately as possible, so that when the transit times were recorded in local time, they could be accurately reduced to within one second of Greenwich time. Not only had the majority of the budget for instruments been spent on transits and altazimuths for this work, but also the majority of the time at the station was taken up by the related observations. Finding the location of the fifteen observation stations would involve a total of 5,000 observations of stellar transits, 800 observations of the moon’s limb and 700 observations of stars for latitude.31 And

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each of these observations, according to Airy’s instructions, was to be reduced twice to ensure the utmost possible accuracy in time. Completing an observation extended much farther than the telescopic observation itself. There was a routine of double-checking and error detection to follow. When recording stellar transits across the meridian, for example, every observation would consist of five or seven timings of the star passing a series of wires. The instrument itself was routinely checked for at least six different possible errors, such as error of level or error of pivot (errors caused by the instrument being out of proper alignment).32 The errors and rates of the transit clock would also have to be continuously measured. And each observer would have been assigned a personal equation. Every precision measurement of a stellar position was refined and verified by a lengthy iterative process of auxiliary measurements and error checks. This pattern of iteration can be seen throughout the many forms of precision measurement undertaken: lunar and stellar transit observations, chronometric and telegraphic time records, photographic measures and eventually Venus transit observations. The strict routine of observation at these far-flung stations was the same as that in large observatories. Historians have described it as part of a general trend towards the new forms of management – division of labour and power concentrated at the top – characteristic of the nineteenth century. But in the context of astronomical expeditions, the role of the routine takes on more significance as a tool for ensuring communication between the stations and Greenwich. The routine was essential both for enforcing similar procedures at all the stations no matter what the local circumstances were and for returning useful, trustworthy results back to Greenwich. After all, once the instrument was dismantled and sent on its way back to Greenwich, most of the instrumental errors would become untraceable. This is why it was so important for each step of error testing and measurement to be recorded on the skeleton forms, so that each and every observation could, in theory, be revisited and examined when the formbooks had returned to Greenwich. Ideally, these forms would provide all that was required for a reliable record of how closely the procedures had been followed. But the validity of the station data also came down to a matter of character and skill assessment – like the ratings of ‘astronomical fitness’ by which Tupman had classified the staff during the training at Greenwich. At Cairo, Browne often described good work as ‘systematic’. Here again is the emphasis on instrumental regularity. Early on he told Airy that ‘Newton is useful and is becoming more so daily, but he has not done much systematic work before’. Regarding the Egyptian astronomer Ismail Bey, Browne wondered ‘if he is to take systematic observations I hope he is to be trusted’. Later on he described Mahmoud Bey, Ismail Bey’s co-worker, as ‘not quite systematic’.33 Browne saw this systematic character as necessary to following the routine of observation, and thus to producing reliable, trustworthy data even under variable or difficult environmental conditions.

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Longitude Experiments When it came to longitude, the requirements of the transit of Venus were particularly suited to take advantage of the century’s ‘communications revolution’. In Airy’s 1857 lecture, he discussed what advantages the nineteenth-century transit programmes had over the troubled attempts in the eighteenth century, and his focus was not on new astronomical instruments: We are in the possession now of two powers, unknown in former times, applicable to this purpose. One is the galvanic telegraph, which possibly (but not very probably) might be laid down in a temporary way. The other is the use of steamers, by which the observers would be distributed to their several posts, and which would be constantly employed for some days before and some days after the transit, in running up and down the line of coast with a number of chronometers, at each post.34

Telegraph lines would be extended to accommodate many of the observation stations, and an effort would be made to complete a round-the-world chain of longitude measures using telegraphy and chronometers. Steamers would be used to carry chronometers from stations to established ports in order to measure the stations’ longitudes. And, since the longer the voyage the longer the time for clocks to stray, cutting back travel time also cut back on the error rates and required quantities of clocks and chronometers. Finding longitude requires somehow carrying along a reference time or absolute time (in Britain, this was time at Greenwich Observatory) to the local destination. Unlike the measurements of local time and latitude, which every station performed in the same way, measurements for longitude were made (or absolute time was carried) differently at nearly every station. Astronomers most commonly measured longitudes by making observations of the moon against the stars and comparing these to the Nautical Almanac tables of the moon’s motion, which gives the time at Greenwich. Comparing Greenwich time with local time will give the current longitude. By the mid-nineteenth century, knowledge of the moon’s motion had become so precise that longitude determination by the lunar distance method was considered by many to be the most precise method available. Both Airy and Urbain Le Verrier had spent the majority of their careers on lunar theory. As was discussed earlier,35 the nineteenth century had seen the degree of accuracy in longitude measures for astronomy far exceed that for navigation and surveying. So, while astronomers had continued to develop the lunar distance method, navigators and surveyors were now using chronometers, which provided a new method that was faster and cheaper but less accurate. Chronometers had become the standard tool for measuring longitude at sea. And from around the 1850s, coastal and land surveys began to experiment with sending time signals via telegraph.

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By and large, telegraphic and chronometric longitude was not accurate enough to be used in astronomy, although observatories had begun to experiment with both methods.36 The transit of Venus expeditions required highly accurate longitude, but both technologies would be applied in experimental new ways. Airy had stipulated that all of the stations were to measure longitude by lunar distances, but some would also perform trials with chronometers, and Browne’s station would make an unprecedented attempt to measure the longitude difference of Cairo and Greenwich via submarine telegraph. In all cases, measuring longitude was a time-consuming process. Airy called the calculation of the station longitudes ‘the most laborious and the most expensive part of the Transit of 1874’ and he had a clear preference for the most laborious of them all – the lunar distance method – even though it could mean extending the duration of an expedition by months.37 The longitudes of Hawaii and Kerguelen Island were found by the lunar distance method. Kerguelen (sometimes called ‘Desolation’) is a rocky outcropping in an empty stretch of the South Indian Ocean, midway between Africa, Antarctica, and Australia. Unlike the other station locales, it was unlikely that Kerguelen would be returned to later for more longitude tests, and no known longitudes were near enough with which to easily compare the island; the closest observatory was in Cape Town. Though the lunar distance method was considered one of the most precise methods available, there was the potentially serious drawback that it depended upon clear weather for the dozens of necessary observations to be made. At Kerguelen, the weather was cloudier than had been expected, and the moon made rare appearances at night, which stranded the British crew for lack of good observations. Stephen Perry, the chief astronomer, described the situation at camp: An excellent run had been made with eight chronometers from the Cape to Kerguelen on the voyage out, and we had already determined by gunpowder flashes the difference of local time between the English observatories at Observatory Bay and Swains’ Haulover, and the American station at Molloy Point … But when longitudes are required correct to a second of time much more than ordinary care must be taken. Our only hope of a sufficiently accurate longitude was from observations of the moon, and so far she had proved herself very disappointing … One hundred double observations of lunar altitude or azimuth, and thirty transits over the meridian, were the numbers required, and the first two lunations had only given us about five transits … Calculations were made on both sides, the question of provisions was weighed against that of lunar observations, and the balance struck was that observations might be continued until the end of February, even though it were necessary to put all on half rations. To be a martyr for science is all very well in contemplation, but all may not find it so agreeable in the practice.38

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Lindsay and Gill’s Chronometric Trials A major part of Lord Lindsay and David Gill’s transit of Venus expedition was designed to test the upper limits of the chronometric method. In order to get more accuracy out of the standard marine chronometer, Gill proposed using a combination of rigorous error and rate (i.e. speed and regularity of the clockworks) testing, combined with a large population of at least fifty chronometers. Typically chronometers offered a relatively cheap way of determining longitude, but with this many instruments, expense became a significant factor.39 The story of Lindsay and Gill’s chronometer experiment begins and ends at the Liverpool Observatory, where the batch of instruments was gathered and tested beforehand, and where they were afterwards returned for further testing. John Hartnup, head of the observatory, was a recognized expert on the problems of regulating chronometers, especially with respect to the relationship between clock rate and temperature change. The growth of the chronometric method in the early nineteenth century had been only partly due to advances in clock technology. Equally important was the development of a system of rate testing, compensation and error correction. Before being set to work on-board a ship, each chronometer would be rated and checked for its ‘clock error’, the rate (in seconds per day) at which it was speeding up or slowing down. This rate would depend upon temperature and humidity as well as the mechanics of the instrument. Normally, around a dozen chronometers would be taken on a long voyage. Each instrument would be set in special mountings to reduce the effect of the ship’s motion, and all would be set together in a designated cabin where the temperature and humidity would be regularly recorded. Clock time would be read frequently, and if some instruments behaved erratically (their rates speeding up and slowing down) or veered from the mean time kept by all the instruments, then those would be dropped. Final mean times would then be gathered from the remaining instruments through a process of weights that favoured the instruments considered most reliable. Most of this rating and testing was done by the chronometer supply firms, which would rent rated chronometers to merchant ships. But as the navy’s need for chronometers increased, more and more chronometer work fell to Greenwich. After 1845, however, most of this work was transferred to the Liverpool Observatory, which had been founded in part to provide chronometer services.40 Each individual instrument – even ones by the same maker – had slightly different ‘temperature coefficients’. At the Liverpool Observatory, facilities for testing instruments in large batches were set up; there was a special underground room that could be kept dry (humidity was a factor as well) and at a cool and steady 55°F; for testing the rates at higher temperatures, there were cases, heated

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by gas jet that could be set at specific temperatures. Gill’s chronometers, for example, were tested at 55°F, 70°F and 85°F, both before and after the voyage.41 Lindsay and Gill took on the task of measuring the longitudes of a host of transit stations around their station on Mauritius. There were British, German, French and Dutch stations, all of whose longitudes were measured with respect to the town of Belmont in Mauritius, which was then linked to stations in Aden, Suez and eventually Cairo. In the end, the longitude work was the only part of Lindsay’s transit of Venus expedition that resulted in publication. Over 500 pages long, the longitude report walks through the procedure and data for all 15 stops in a network of locations connecting Liverpool, the Nile Delta, the coast of Madagascar, Bombay, Berlin and Greenwich. In most cases, the connection of longitude was made through comparing Gill’s shipload of chronometers with the local time at each spot. Based on this experience, Lindsay and Gill presented some recommendations for the future use of the chronometric method in astronomy. One of their main points was that a clock must be ‘aged’ before it can be used for precision work: Given a new spring, a chronometer rate would accelerate by about 4s daily for a few years, then gradually diminished towards zero. The chronometer is now at its best, and continues so for years … in the early stages of this acceleration chronometers never go steadily; their rates are liable to sudden change. This fact is so well recognised that the best makers never issue their chronometers till they have been going for a couple of years – until they ‘settle down’ as the technical phrase is … and perhaps a safe rule, if it could be carried out in the future, would be that no chronometer should be used for accurate longitude operations until it is six years old.42

This six-year ‘ageing’ process for chronometers is perhaps the best exemplar of the nineteenth-century brute-force style of achieving precision via error management and analysis rather than error reduction. Lindsay and Gill had demonstrated that the chronometric method was suitable for accurate astronomical work. But this method would not go on to become widely used in astronomy. This was probably due, in the most part, to the growth of an even cheaper and faster method, telegraphy, which was only just gaining credibility at the time of the transit expeditions.

Browne’s Experiment in Submarine Telegraphy In the early 1870s, telegraph lines were rapidly spreading out from Britain towards Africa and Asia. Cairo and London had been connected by telegraph in 1872, giving the transit of Venus stations in Egypt the option of trying to determine the longitude difference with Greenwich by exchanging time signals. The method had been performed successfully on overland wires as early as 1844, but

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the exchange of signals between Cairo and London would be a new challenge. The requirements for accuracy were greater, and this was a submarine cable, longer and thinner than the transatlantic cable, the only other submarine cable over which time signals had ever been successfully sent. As with the chronometric longitude method, Airy was characteristically sceptical that the results would be accurate enough, but he agreed to give it a try.43 The control of the international submarine cables was entirely private, in contrast to Britain’s landlines, which had been taken under state control in 1868. Thus it was to the board of directors of the Eastern Telegraph Company (ETC), then Britain’s largest submarine cable company, that Airy had to appeal for help in determining the longitude of Cairo and Suez. On the part of the company, agreeing to help the transit enterprise meant giving away many hours of cable traffic time that otherwise would have been spent generating cash. Nevertheless, it agreed not only to lend the lines but also to help develop the system of signal transmission and reception. In the end, the lines would be given over for transit experiments on four evenings in the autumn of 1874. The company was making roughly £10,000 per day by delivering around 2,500 messages costing about £4 each. Altogether, these sessions would likely have cost the company over £4,000 in profits – nearly as much as the entire transit photographic programme.44 From its base station within the cliffs of Porthcurno in Cornwall, the ETC controlled cables to the United States and through the Mediterranean to the Middle East, India and China. It was at Porthcurno that most of the preparation and experimentation for the transit telegraphy was done.45 Determining the longitude of Cairo presented certain challenges to both the astronomers and the telegraphic engineers. For the engineers, the task was to form a direct link to Alexandria. Because of the weakness of the submarine signals (and the lack of amplifying circuits), a telegram from Egypt to Britain would normally be passed through four ‘relay stations’ where the messages would be received and manually retransmitted to the next segment. But for the purposes of sending time signals there had to be an uninterrupted transmission. So the five cables comprising the relay route were temporarily ‘joined up’ – Porthcurno to Vigo, Lisbon, Gibraltar, Malta and Alexandria – by connecting the lines at each station. The length of this ‘joined up’ wire was 3,700 miles, a worrying 730 miles longer than the transatlantic cable. It also had a much smaller copper section (through which the signal passed), weighing just over a quarter of the weight of the transatlantic cable, which had been used in 1866 to determine the longitude difference of London and Washington.46 For the astronomers, the greatest concern was that the signals would not be strong or distinct enough to be useful for the precision second-ticks required. In order to test what the signal would be like, experiments were performed on a ‘model’ submarine cable. Cromwell Varley, a well-known ETC engineer

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(and a well-known spiritualist), ‘kindly lent his artificial cable, consisting of a large resisting coil and apparatus, by which preliminary practice was obtained at Greenwich in the special character of signal required’.47 These experiments confirmed that a signal was detectable through such a length of wire, but it was extremely weak. What was needed was an extremely sensitive signal receiver. Generally the ETC used mirror galvanometers as receivers. These instruments served to magnify the submarine signals, which were always relatively weak, by attaching a mirror to the coils that rotated in response to signals. When light was reflected off these mirrors, the rotation could be seen much more clearly. An even more sensitive apparatus had recently been developed by J. J. Thompson called the siphon recorder. This instrument also had the important benefit of being a ‘speaking’ recorder as it was called – one that used an ink stylus and so wrote out the message. But the transit telegraphy signals were also too weak to be received by this instrument. John Bull, superintendent of the receiving station at Porthcurno, found a solution. The siphon recorder was so called because it used a very light stylus that was siphon-fed ink from a well. This would have been attached to a fine wire, suspended between two electromagnets, that moved in response to current changes. What Bull did was to replace the siphon and stylus with an even lighter fragment of mirror, thus turning it into a highly sensitive version of the mirror galvanometer.48 As for the kind of signals that were to be sent between Cairo and Greenwich, the stations would alternate transmitting sidereal and solar local time. Because sidereal time slowly gains on solar time by about a second every six minutes, if a sidereal clock and a solar clock are placed side by side, they will tick in unison once every six minutes, at a moment that can be accurately calculated. If the sender were to transmit second beats from a sidereal clock, the receiver would listen for the coincidence of beats between these signals and his local solar clock, which would give a moment of synchrony between the foreign sidereal and local solar time, precise to within a second.49 From that, the difference in local times could be calculated. As the 1874 letter books from the Malta station record, the joining of lines for the ‘Astronomer Royal’s experiments’ was not an immediate success, and it took repeated effort just to orchestrate the joining of the cables on the right days at the right time.50 But eventually signals were sent over the uninterrupted cable, and they were strong enough to be detected with clarity by Bull’s modified speaking recorder. After a long series of exchanges in November of 1874 (in all, 956 signals were ‘observed’),51 Airy was satisfied with the results of the submarine telegraphic longitude and agreed to use them as the primary longitude measure. Browne then happily abandoned the observations for longitude by lunar distances and began the much more straightforward process of telegraphing signals (on the Khedive-supplied land lines) between Mokattam and Thebes,

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Luxor and Suez.52 From Suez, the longitude differences of the Madagascar-area stations would eventually be compared via Gill’s shipful of chronometers. For Browne, a final longitude challenge was that of the Cairo Observatory. The building itself, erected by the previous Khedive, was part of a larger military establishment in the hills above the city to the north. According to Browne, the observatory was infrequently used and in decline. It had two full-time staff (Ismail Bey and Mahmoud Bey) and a set of good observing instruments, but no transit clock, and its longitude had not yet been determined. Hence Browne’s gift of the Dent clock. Browne told Airy that he had offered not only to install the new clock at the observatory but also to work with Mahmoud Bey to determine its longitude difference from the Mokattam Hills station, and thus from Greenwich. As the Cairo Observatory was visible from the Mokattam station, the plan was to flash time signals between the Mokattam station and the observatory using parabolic mirrors and lamps. Light signals (using gunpowder) had similarly been used on Kerguelen between the French, American and British stations.53 Signal exchanges between Mokattam and the observatory were scheduled on several different nights in December, but something went wrong each time. One night, Browne and Newton were expecting signals from Mahmoud Bey, but they did not come. Another night, Browne says he was caught by surprise when flashes of light began emanating from the Observatory. And he says other attempts were foiled by various misunderstandings regarding the routine for sending and receiving signals. Bey was, according to Browne, ‘not quite systematic’, though this of course is only one side of the story.54 For whatever reason, the Egyptian and British astronomers were unable to collaborate. In the end, the Cairo Observatory, though just kilometres away, was left outside of the region’s new network of longitude measurements that the transit expeditions were to leave behind.

The Day of the Transit: 8–9 December 1874 At the centre of the entire enterprise were the few crucial hours of the transit of Venus. Here the result of more than five years of preparation would be played out at over 75 stations across the globe, and the conditions would be set for many more years to come of calculation, analysis and debate. Hawaii was the first region to view the transit, where internal contact was to be observed a few hours before sunset. There were three camps distributed around the islands. At one of these, where George Forbes was in charge, clouds blocked the view of contact, but at the other two stations the weather was clear. George Tupman was at the main camp in Honolulu. His report conveys the

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excitement, pressure and surprise that many observers experienced during the few crucial minutes of internal contact: When I judged that about five minutes remained before internal contact I began to measure the cusps [the portions of the sun’s edge separated by the encroaching silhouette of Venus], Mr. Clapp was counting aloud the seconds from the clock … I placed the two images in coincidence to estimate the time remaining before internal contact. This I had frequently practised on the model, and generally was not more than 10 seconds in error. I remarked aloud to Mr. Clapp that it wanted a minute … Up to this time the circumstances of the Ingress of Venus exactly resembled those seen in the model. I drew out the micrometer at 20h 45m 43s, laid it on the shelf, and inserted the negative eye-piece power 150, down to the pencil mark on it for focus. This I had repeatedly practised on the model, and always effected in 10 or 12 seconds. I was no longer than usual on this occasion. On looking in I saw the cusps separated such a distance that I thought it still wanted 30 seconds of contact, but the image not being perfectly sharp I threw it out of focus with the rack motion, and brought it carefully in again. As I did so I perceived that the cusps were united by a narrow band or thread of light of sensible width, but faint, and instantly called “contact” though fearing I had missed it while focusing. As the appearance at that instant made a vivid impression on my mind I afterwards made a drawing of it. Everything hitherto having so closely resembled the appearances in the model, I felt certain that I had missed the contact while focusing, although I could not understand how it could have occurred so much sooner than I had expected … I was surprised that the band of light did not change much in appearance for some time; it seemed a long time in comparison with the model experience. There was no black drop nor ligament. The planet was perfectly circular, and nothing whatever disturbed the sharpness of its outline at the place of contact. The band of light gradually and imperceptibly brightened, and as Mr. Clapp said ‘twenty’ … the general appearance was similar to the model a second or two after contact. At the 20 seconds which I have recorded I am perfectly certain that the contact was passed, established completely – not ‘contact’ properly speaking, for that implies some definite instant which was never observed. At that time, and for a second or two before, there was the shadow on the light at the point of contact, a phenomenon always seen with the model, but nothing like a ligament or black drop, although I looked carefully for such an appearance.55

Completely rattled, Tupman believed he somehow missed the crucial ‘instant moment which never happened’. He complained that contact had happened faster than in the model, but at the same time the appearances of the phenomenon changed more slowly (‘imperceptibly’) than he was used to seeing. He saw no black drop effect. The drawing accompanying his report, strikingly different from the eighteenth-century drawings of contact, shows a clearly defined and regular silhouette, with a slim band of light separating it from the arm of the sun. The other observer at Honolulu, Lieutenant Noble, reported ‘There was no black drop – no ligament, but a rough dark shade which gradually faded off to a thin tint corresponding to the phenomena I had observed in the model. This,

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instead of being nearly instantaneous, as the model generally showed, extended over some 20 seconds.’56 Tupman’s and Noble’s reports (which will be returned to later) are typical of the rest of the observations – many comparisons to the model are made, and the general impression is of very slow, very gradual change that did not correspond to the black drop effect they had come to expect from the model practice. The clarity of contact was not, however, received as good news. Photography was mostly successful in Hawaii. A good series was captured with the Honolulu photoheliograph, but, as a Honolulu newspaper chided, ‘The famous Janssen revolving slide unfortunately failed on account of the difficulty of pointing’. In many of the plates, the silhouette of Venus was somewhere just outside the picture frame. In the town of Honolulu, the transit was a spectacular public event. The same newspaper reported: At a few minutes past three, you could see everywhere in the streets, faces looking upward to the sun with a piece of shaded glass in hand to screen his fierce rays from man’s weak, yet ambitious, searching eyes. A minute or two elapsed … Another minute … Ha! ‘aia la!’ there it is cries one keen sighted close watching kanaka … as the clearly defined acula upon the [ruddy] plane is now distinctly seen by every eye an enthusiastic native says ‘surely they who behold this were prophets, and Lono was a prophet.’ But we must turn to where the real star prophets were at work … we find the indefatigable chief captain Tupman gazing sunwards …57

The next station to fall within the path of visibility was New Zealand, where ingress was also to be observed. Here, clouds blocked visibility almost completely, and only twenty-two photographs were taken. In Australia, where observations were made at the government observatories in Sydney and Melbourne, clear skies prevailed. Generally, no black drop was reported, and at Sydney, where a transit model had been used for training, there was the feeling of having been deceived by the artificial transit: For second contact [first internal contact] I think there can be no doubt that different phases of the phenomenon were taken by observers according to the different effects produced by the ghost of the black drop, which up to that time had a very tangible existence for all of us, not only from what we had read about it, but from seeing it so constantly in the artificial transit … for the third and really most important phase [that is, the second internal contact] we had all fortunately learned to disbelieve in black drops …58

Next came India, where the photographic expedition at Roorkee was being run by Tennant, who reported, ‘The contact took place without any black drop or distortion … I had been led to expect’. His companions also recorded no black drop or distortion. ‘Some time was now spent in discussing the appearances at contact and in sending a telegram to Captain Strahan [a private observer] at

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Lahore, warning him that probably he would not see the phenomena which had been seen in the model.’ Tennant reported to Airy that he had made 100 photographs of the transit.59 The Indian government also supported observers in Karachi, Madras and Calcutta. In Kerguelen, at Father Perry’s main station on Observatory Bay, clouds partially obscured ingress but cleared completely for egress. At the station on Rodriguez, the skies were clear, as they were for Lord Lindsay’s expedition nearby on Mauritius. And finally, throughout Egypt, where egress was visible just after sunrise, the sky was clear.

The Transit of Venus Observed in Cairo At the Mokattam Hills station, observations of egress commenced soon after sunrise. Browne would later tell Airy that he felt the model practice had been invaluable; at times, he said, he could not convince himself it was not in fact the model he was watching. But as with all of the observers, some important aspects of the transit took them by surprise. Most striking was a narrow ‘thread of light’ around the edge of the planet that was taken to be an effect of the Venusian atmosphere. This thread of light had also been reported at some of the other stations. According to Browne, all of the station observers saw the ‘thread of light’. He was anxious to point out that each observer had carefully written up their own impressions before talking them over as a group. As for the black drop effect, Browne and Newton reported seeing a subtle but distinct effect. The nature of the black drop – its intensity, colour, shape and very existence – was immediately a subject of debate at the station, and after the transit, they returned to the model to make further comparisons. Though roughly half of the British observers would report seeing some kind of black drop effect, in Cairo there seems to have been the strongest similarity between the transit and the model. This, as Airy would later speculate, may have been due to the low elevation of the sun at the time of contact in Cairo, when atmospheric effects may have created a more pronounced black drop effect than at the other stations. Browne’s other surprise of the day was that one of the women at camp, Emily Newton, who was observing with a spare telescope, apparently turned out to be a very competent observer. Quite unexpectedly, her timing of contact came very close to that of Browne’s: Miss Newton observed with a telescope of her brother’s (about 3 inches) She had been carefully drilled by me on the model together with the other young lady [Miss Adelis] whom I mentioned we had put up in Camp and whom I posted at the Altazimuth on a stone. Both saw the phases and were valuable in saying just what they saw. There was a chronometer between them where both could see it. Miss Adelis failed

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The Transit of Venus to keep count, but Miss Newton recorded contact at a chronometer which reduces nearly the mean between her brother’s observations and my own which may be said to stand nearly as follows: Browne with Lee … … … … … 13.22.24 Newton with De la Rue … … … 13.22.20.7 Miss Newton with 3-in … … … 13.22.22.9

Although the aim had been for observers side by side to record contact within a second of each other, the close agreement between the three Mokattam observers was still remarkable. The problem, Browne knew, was that, as a woman and an unofficial observer, Emily Newton’s competency would be suspect. Did she not, perhaps, hear others call contact and simply follow along? Browne thought not: The only reserve to make in using of [Emily Newton’s contact observation] is the objection that had it been very widely different we might probably have assumed the chronometer counting had been too much for her and not noticed her observations at all. This objection is true as far as it goes, but considering the reduction that was necessary to her chronometer time and the impossibility of her being influenced in any way by hearing my wife’s repeated seconds … I think her observation very valuable.60

It was an awkward situation from the perspective of correct procedure. To use an observer’s data only if it corresponded closely with an expected value would be, as Charles Babbage had called it, to ‘cook the books’.61 Even more awkward was Emily’s gender; this was the real issue. In the late nineteenth century women were literally excluded from most science in Britain. Societies were restricted to men, and women often were not allowed to attend general public meetings. The new evolutionary theory was commonly taken by leading figures – including Darwin himself and T. H. Huxley – as an explanation of the perceived cognitive inferiority of women and even more specifically of why it was unnatural for women to participate in science.62 What to do then with a woman’s potentially very useful transit of Venus observations? In the section of The Decline of Science on ‘cooking the books’, Babbage wrote that ‘the character of an observer, as of a woman, if doubted, is destroyed’.63 Indeed Emily Newton’s observations were a target for double-strength doubt. Browne, however, motivated by the potential value of her observations (as a sign of the veracity of his own), succeeded in arguing the point. He tried to build the case that Emily Newton should be considered a reliable, even experienced, observer. Not only did he point out her training on the model (which he had never mentioned before) but also offered Airy aspects of her character that indicated she might as well have been taken seriously all along: With regard to Miss Newton she has before worked a good deal at gazing with a telescope and is one of the most clear headed young ladies I ever met. She will take

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nothing for granted and insists on not understanding any thing till it is quite clear to her. I should like you to meet her and talk to her and I think you will be satisfied that she is a good observer. If you had seen the way she would want to understand the meaning of the process of working out logarithms you would be satisfied of her ability. She is not the least shy and I think you would acquit her of waiting till her bonnet or dress was finished before sailing.64

In the end, Emily Newton’s observation of contact at egress was accepted as valid. She would be the only female observer mentioned in any official publication of any nation on the transits of 1874 or 1882. It had been expected that the observations of Mahmoud Bey and Ismail Bey would also be included in the data from Browne’s station. But Ismail Bey did not come to the camp on the day of the transit, and Mahmoud Bey’s observations from the Cairo Observatory depended upon getting the longitude of that observatory, which had yet to be successfully measured. Immediately after the transit Browne telegraphed preliminary results back to Greenwich, and also to Reuters and American news services. The next day he sent off a longer letter to Airy, as well as letters to the Times of London and the Engineer. In the city of Cairo, according to Browne, ‘Great numbers of people saw the transit, especially I hear ladies in the harems of the Princess (Said Pacha’s widow) and others who had elaborate screens of dark glass and were delighted’. He had explained the purpose of the expedition and the black drop effect to the Khedive and some of his sons, who also observed it. Afterwards, the Khedive told Browne he thought he had observed the black drop within a few moments of Browne’s own observations, but Browne worried that ‘in my bad French I failed to explain the black drop’.65 Princess Said, who had befriended Mrs Browne, had obtained a telescope for the occasion. She saw the black drop and made a painting of it, which Browne was extremely curious to see. ‘It would be interesting to see the unprejudiced impression of a … circassian lady of superiour mind but who has been kept inside Harem walls all her life’. In general Browne was keen to know the ‘unbiased’ impressions of the black drop effect held by non-astronomers in the area. He was quite excited to see this rendering from what he obviously considered to be an ideally unbiased observer. But he was to be disappointed. Eventually the painting was given to Mrs Browne in exchange for a photograph of the transit. Deflated, Browne described the painting as ‘quaint … like scene painting … [but with] no astronomical value however I fear’.66 Aside from where there was poor weather in New Zealand and in parts of Kerguelen, the observations of the 1874 transit of Venus were generally said to have been a success. The real surprise had been the phenomena of contact, which many observers felt had been misrepresented in the model. The black drop presented less of a problem than had been expected, and this threatened to present

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a whole new set of issues, which Airy, back at Greenwich, was already preparing to face.

Worldwide Spectacle: The Day of the Transit in the Press Eight months elapsed after the Transit of 1769 before the diagrams and calculations made by the scientific members of Cook’s expedition were known in England. By the aid of the then undreamt-of telegraph we already know the successful result of many of the observations made in widely different places two days since. The Irish Times (Dublin), 11 December 1874 In the midst of these [ramblings] the editor pops his head into the door and says he thinks I ought to knock something comic out of Venus. I ask in what way? … I turn to my classical dictionary and find that Venus was by no means the moral woman she ought to have been, and I am a little surprised at the Sun allowing her to cross his path. The New Zealand Herald (Auckland), 9 December 1874

Cheap print media, telegraphy and steam-powered mailers ensured that news of the transit of Venus circulated rapidly throughout the British empire and beyond. For a few days around 8–9 December, the transit of Venus was frontpage news in every major European-language newspaper, and in many regions on the imperial periphery. Sometimes these were a few columns repeated and rehashed from either science periodicals or newswire services such as Reuters. For example, some of the stories from the London Daily News correspondent covering the Egyptian station were also repeated in newspapers in Allahabad. Wires from the New York Herald correspondent that followed the American expedition to Nagasaki were also printed (and in this case lampooned) in the Irish Times.67 Longer articles would typically begin with potted histories of the transits of Venus, followed by a description of the methods involved in measuring the sun’s distance. At places where the transit of Venus was visible, there would usually be instructions for how to observe the transit, which always stressed the need to protect the eyes when looking at the sun, for example with ‘deeply coloured glass – especially a piece of deep red and deep green or deep blue together – or smoked glass’, sometimes giving instructions for how to properly smoke window-pane glass.68 Even where the transit was not visible, the amount of space often given to technical exposition is striking. From a twenty-first-century perspective, these descriptions are surprisingly detailed, technical and heavy on astronomical ‘jargon’. Today’s newspapers strenuously avoid technical terms and rarely describe even the most general mathematics behind scientific events or pursuits. The same was not true in 1874. For example, the North China Daily News of Shanghai describes the passage of Venus across the sun thus:

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When Venus, at her inferior conjunction, as she moves in her orbit round the Sun, passing between the Earth and the Sun, has less latitude or distance from the Ecliptic than the Sun’s semi-diameter, and will therefore be within the Sun’s disc. The apparent motion of the planet being then retrograde, it will appear to move across the disc from East to West, in a line sensibly parallel to the Ecliptic.

The newspaper article also points its readers to appendices and specific pages of the Nautical Almanac where exact equations for calculating the specific hour and minute of the transit as seen from Shanghai could be found.69 Given that many readers of any English-language daily at a trading port such as Shanghai would have been seamen with some training in naval astronomy, perhaps that technical style should not be surprising. But even in the London papers and in non-scientific periodicals, the typical transit article contains much more technically-rich descriptions of the transit method than we would see today. Another popular subject involved ruminating over what was the point of ‘abstruse’ or ‘purely speculative’ research such as the transit.70 Often, however, the aim of refining the sun’s distance would incorrectly be connected to ‘further increas[ing] the facilities for ascertaining longitudes, defining boundaries, and perfecting the art of navigation’.71 These more fundamental misrepresentations contrast strangely with the technically-detailed style of presentation. Whether this reflects on the general astronomical knowledge of the population, on the desire to fill space in the many new cheap broadsides, or on something else entirely remains to be discovered. In London, the event was generally treated with more gravity than it was elsewhere. (Some Dublin papers, in particular, clearly approached the subject which much less of a sombre, awe-stricken tone.) On the day after the transit of 1874, The Times of London took the opportunity to reflect on the differences between the eighteenth- and nineteenth-century transit expeditions. The focus of the article was not, as might be expected, on the technological progress represented by, for example, photography or telegraphy, nor was it on the impressively large scale of the nineteenth-century enterprise. Rather, the article examined in detail the global demographics of the participating countries – who had participated in past transits and who was engaged in the current programme – and it stressed how this mirrored the broader patterns of change in world politics. Since the previous transits, as the article goes, the Dutch empire had faded, America was on the rise, and the old powers France and Britain were working hard to maintain their dominant positions. And all of this was reflected in the constitution of the world’s 1874 expeditions. The article concludes with a lesson on the central role that scientific ambition had played in leading nations, and civilization, forward. It is really a lesson on how and why Britain is still at the top of the heap. The point is to reinforce Britain’s own self-regard as the leading source of scientific and technological advancement, and to warn that ‘abstract’ scientific investigation such as the transit is a key, even a central, ingredient in maintaining and developing the British empire:

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The Transit of Venus It is a proper subject of national pride that the benefits derived by the world from the invention of the steam-engine and the electric telegraph, and from the various applications of chymistry to the industrial arts, have all, until the last few years radiated from England. We here have the secret of a large part of England’s riches and England’s strength. But it is useless to hope that the mere knowledge of the acquired facts of science will furnish that new weapon which nations are now adding to the sword to enforce their superiority. The mental soil which produces new ideas for a nation’s use can only be cultivated by the discipline of scientific investigation. Further, it cannot be doubted that, as modern civilization is still further developed, the new ideas which a nation produces and throws into a concrete form will be among the most valuable of its exports, because each nation will work up the old ideas for itself.72

This is the historical scientific jingoism of the transits at its peak. It is a surprisingly robust outline of the role science and industry has played – or rather should according to the article be understood as having played – in the shared national history. Again, this is an approach to nation-building that Ernest Renan was describing in 1882: To have common glories in the past and to have a common will in the present; to have performed great deeds together, to wish to perform still more – these are the essential conditions for being a people. One loves in proportion to the sacrifices to which one has consented, and in proportion to the ills that one has suffered. One loves the house that one has built and that one has handed down.73

This article from The Times on the day after the transit is one of the best illustrations of how the transit enterprise had come to represent a vivid, if fleeting, symbol of the strength of British science. While the Victorian transit programme was held up as an example of the importance of state-funded abstract scientific investigation, ironically, the transit enterprise would turn out to be a poor representative of not just state science but of scientific progress in general.74 As we will see, in this particular case, the capabilities of precise measurement made very little progress across a century otherwise marked by rapid scientific and technological development.

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Table 1. Transit of Venus 1874: British Stations and Personnel. Asterisks indicate people who were not officially members of the expeditions.

REGION Egypt

STATION Cairo

Thebes

Sandwich Islands [Hawaii]

Kerguelen

Capt. W. A. Orde Browne (late RA) Mrs Orde Browne* Mr Newton Miss Emily Newton* Capt. Abney, RE Colonel Campbell* Mrs Campbell*

Suez Honolulu

Mr Hunter Capt. G. L. Tupman, RMA. Lieut. Ramsden, RN Capt. Noble, RMA Capt. Eaton, RN*

Hawaii

Professor George Forbes Mr Barnacle

Atooi

Mr Johnson Rev. Dunn* Lieut. Neate, RN Lieut. Hoggan, RN Mr Burton Com. Wharton, RN* Major Palmer, RE Lieut. L. Darwin, RE

Rodrigues

New Zealand

OBSERVERS

Burnham

Naseby

Lieut Crawford, RN

Royal Sound

Rev. J. Perry Rev. Sidegreaves

Port Palliser

Mr T. Smith Lieut. Goodridge, RN Lieut. Corbet, RN Lieut. Coke, RN

PHOTOGRAPHIC ASSISTANTS

Sapper Laffeaty 2nd Corpl. Mitre Sapper W. Farr Sapper M. Meins Sapper G. Currey Sapper W. Myers

Sapper F. Taylor Sapper T. Currie Corporal Sharp 2nd Corpl. White Sapper G. Higgins Sapper Hilbert Corporal Wright Lance Corp. Wilson

6 THE OUTCOME

For a few months after the transit, newspapers and journals regularly followed updates from the expeditions. Airy apparently sent updates to the press; one list of places to which transit of Venus information should be sent included, among government offices and national observatories, the following: Reuters’ office, the Times, the Daily News, the Standard, the Daily Telegraph, the Athenaeum, Nature, the Smithsonian Institute, the Manchester Courier, the Pall Mall Gazette, the Echo and the Globe.1 But, in general, press coverage of the enterprise did not last long after the day of the transit. There were a few last attempts to draw some public reaction by reporting spectacular failures, such as a report in the Daily News from mid-January 1875. The supposed disaster caused by the loss of observations in New Zealand and Kerguelen was contrasted with the supposed successes of Lord Lindsay’s operation, especially his choice of the ‘almost perfect, theoretically’ long-focus photographic method, which, as the paper suggested, Airy declined out of pride to adopt: The occasion was far too important to be played with; and still less excusable than mere carelessness would be any neglect arising from unwillingness to advance schemes suggested by others. We are thinking rather of the future judgment of the scientific world than of any immediate or official reprehension – the latter, indeed, official scientists are secured from in this country.2

Proctor had written in the Daily News before and he may well have been the author of this piece; the concluding jab at Airy’s alleged immunity is characteristic of his style. Either way, it was far too early to make any statements about the relative successes of each country, or about how the British government would react to any failures. While it was true that the Americans had had slightly better luck with the weather, other factors would be much more important in deciding the fate of the research programmes. Foremost among these factors was the state of the data itself. Airy, who excelled at organizing the precision measurement of stellar meridian crossings and other exact observations of star positions, was about to enter a protracted struggle with what was surely some of the most imprecise, vague and problematic data that he had ever – 119 –

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Figure 13. A printed (5 inches x 5 inches) glass plate collodio-albumen photograph of the transit of Venus from the 1874 British programme. Note that the measurement work was done on plates just like these, except that they would have been negatives (see Figure 14). Also note that this image is rotated – the silhouette of the planet crossed from the upper-left to the upper-right edge of the sun. Reproduced by permission of the STFT (Science and Technology Facilities Council).

Figure 14. Six of the original 1874 transit of Venus glass plate negatives. Each plate is about 5 inches x 5 inches. There is a lot of variation in the colours and textures in the photographic emulsion. Reproduced by permission of the STFT (Science and Technology Facilities Council).

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dealt with. The photographic plates and the observational reports would each present their own challenges, but, essentially, the problem with both forms of data was the same: no matter what analytical tools were used, no clear result could be drawn. The state of the data itself was, of course, largely a result of the decisions made during the preparations. Some of the debates about transit methods that were covered in Chapter 2, especially those concerning the photographic methods, continued to simmer after the transit, finally reaching a resolution towards the end of the 1870s. Likewise, the results of the experiment in model training would also become apparent during the analysis of the observer reports. If the nature of the data had set the parameters for what parallax result could ultimately be achieved, it was management and funding that would determine how far Airy and his staff would go towards achieving the best possible result. Money was a crucial factor in decisions about which avenues of research to pursue. The government’s support of the transit programme also declined sharply post-transit, and the calculations would proceed under much greater financial pressure than had the preparations or expeditions. Airy’s decisions about how to approach the data also played a crucial role. He relied much less on advice during the calculation phase, even on issues related to photography.

Airy’s International Proposal for Reducing the Observations As we saw in Chapter 4, the preparation phase of the transit enterprise had been a challenge for Airy. Photography, the question of the black drop effect, and even the use of the model to train observers, were all new territory from the perspective of the Greenwich routine. Often in doubt about how to proceed, Airy turned to advisors such as De La Rue, Abney and Tupman, who shaped the design of the programme more than Airy himself. During the expeditions, Airy’s role back at Greenwich was even more marginal; he was a shadow authority figure to whom the expeditions would all eventually have to report. Now, after the transit, when all that remained was astronomical data – lots of it – to be reduced and combined, Airy was again in his element. His reputation as a scientist had always rested on his theoretical and mathematical work. Allan Chapman, who is especially interested in drawing a picture of Airy ‘as a human being’, believes the key to Airy’s ‘mind and motivation’ was ‘a capacity for creatively handling vast quantities of technical data, extracting, and then lucidly communicating, the general principles drawn therefrom’.3 With a huge mass of data awaiting analysis, it was time for Airy to apply his mathematical rather than his managerial talent to the transit programme. In early January 1875, while Browne’s wife was selling the camp furniture in Cairo, Tupman was auctioning off supplies in Honolulu, and the rest of the expeditions were likewise preparing to return, Airy began to work out a plan for reducing the observations. Published in March, the plan described the method

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of reduction that not just Britain but – it was hoped – all of the participating countries would follow. Although the calculations involved were, as Airy said, nothing new, the task had its own challenge: Different nations and different observers are concerned in the observations; different theoretical views have animated the astronomers who have selected the stations, and planned the observations; instruments of different classes have been employed; different elements have been the subject of observation.4

Here was a plan to unite it all. He even went so far as to offer guidelines for font and paper sizes so that the results could easily be bound together into a single series. Unlike the experimental techniques used in observing the transit, Airy’s plan for the data analysis was to employ standard, established methods of error theory and data combination. The plan had two steps: the calculations for each observation, and the combination of observations into a final result. First, for each observation, the data would be converted into a form expressing the distance

Figure 15. A page of the final illustrations for the observations at Cairo, based on observer drawings of the appearances at contact. From G. B. Airy (ed.), Account of Observations of the Transit of Venus, 1874, December 8, Made under the Authority of the British Government, and of the Reduction of the Observations (London: Her Majesty’s Stationery Office, 1881). Reproduced by permission of the Bodleian Library, University of Oxford.

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between the centre of Venus and the centre of the sun. The process involved taking the calculated, or predicted (‘tabular’), values for the particular positions of the sun and Venus, and comparing them to the observational data. From the difference of these two figures, the calculations would be adjusted and values produced for that location of the apparent positions of Venus and the sun at each station, expressed in the form of the distance between their centres. The tabular positions and distances would be based on an ephemeris, published as a special section of the Nautical Almanac, containing tables of the positions of Venus and the sun to within 0˝.01 for every ten seconds during thirty minutes or so on either side of contacts, and for about every minute for the entire duration of the transit. The tabular values were considered liable to error, and the transit observations were expected to provide a correction for not only the solar parallax, but also a number of other figures such as the right ascension (RA) and north polar distance (NPD) of Venus. When the observations were ready for combination, the results would take the form of five separate equations – the ‘Final Equations’ – providing the corrected values to each of the tabular values involved (RA and NPD of the sun, the sun’s angular radius, the equatorial horizontal parallax of the sun and of Venus, the RA and NPD of the centre of Venus, and the angular radius of Venus). Finally, they would be ready for comparison with other stations to produce values for parallax. By pairing the stations in different ways, each country could produce several values for parallax. All of these values would then be combined together, either by using a weighted average or by the method of least squares, giving the result considered most accurate. As mentioned earlier, Airy’s instructions continued through to the publication and the printing details. According to his plan, the observations of each national expedition were to be published under the superintendence of the head of the expedition and distributed as soon as possible. The reports were to contain histories of the expeditions, the persons involved, and maps giving exact locations of the expedition camps. Most importantly, for anything that bore upon the actual observations – the descriptions of contact, the ‘impressions’ of the observers, micrometer-measures, measures of the photographs, etc. – descriptions were to be given in the fullest detail. And the final depository for the instruments and official documents relating to the expeditions was to be clearly indicated, in case future astronomers would be as interested in this transit as the nineteenth-century astronomers had been in those of the eighteenth century. Airy had an ambitiously international vision of the outcome of the 1874 transit of Venus enterprise. He saw it in its grandest possible form: all of the data from all of the countries uniformly produced and bound together under one massive series, which, at the very end, would unite all of the work into one conclusive value for the sun’s distance. As for who would manage it all, Airy hoped

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that an ‘astronomer of eminence’ (though not himself as he made clear) would superintend the assembly.5 However, although all of the participating countries seemed to agree on the outlines of Airy’s programme and would follow it in their reports, none ever committed to the full project.

Calculating Parallax in 1874 versus 1769 There are some important differences between how the data was to be handled for the transit of 1874 and how it had been done for the transits of 1761 and 1769. These differences reflect how error theory and data processing had changed since the late-eighteenth century.6 One of the most fundamental developments came with the growing popularity of the method of least squares, which was employed at various stages throughout the 1874 calculations. It had been a common tool for astronomers since the 1830s.7 In the transit, it was used, for example, to quantify how well a certain parallax value would ‘fit’ each of the observations used to produce it. Yet another difference was in the use of weighted means. Before combining observations, a weight would be assigned to each one according to its ‘merit’: ‘Every individual observation will then have an influence proportional to its merit; and reason, as well as formula, leads us to think that the best final result will thus be obtained’.8 The higher the weight of an observation, the greater its impact on the mean. Not surprisingly, the weighting of observations would be one of the most contested aspects of the calculation. In the 1770s, weights were not applied to observations. Rather, questionable observations were discarded, and the mean was then derived only from observations that were considered strong. These two different approaches reflect what some historians have seen as a fundamental shift in the conception of error that occurred during this period.9 In the eighteenth century, it was thought that by combining results, errors would contaminate the final result, multiplying not compensating, so it was important to select the observations carefully. By the early nineteenth century, this attitude had given way to a more probabilistic idea that errors, if non-systematic, would be random and would therefore, in a large data set, tend to cancel each other out. On this view, the larger the data set, the lower the residual error, so as many observations as possible should be used. The tendency to favour large data sets is evident throughout the transit programme, from longitude calculations to the photographic measurements. Zeno Swijtink argues that this attitude had gained special force in the late ninteenth century, when the development of statistical tools such as the method of least squares and the ‘theory of instruments’ (the focus on instrumental error) were a product of and a catalyst for a great upsurge of ‘precise numerical determinations and precise quantitative predictions’.10

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One last nineteenth-century development was the practice of assigning a ‘probable error’ to the results. This was a measure of the reliability of the most probable value.11 When the method of least squares was used, the probable error was of central importance, and it was also calculated for results that had been obtained through weighted averages. Generally, a large probable error was considered a sign of little procedural control, and thus of a poorly executed observation programme. According to Airy, this would be the most difficult step in producing the final result of solar parallax. Often the real failure of the British programme would reveal itself in the sizeable probable error assigned to the results.

The Plan to Measure the Photographs On 17 December 1874, when the London Graphic featured an article on the ‘Sham Transit of Venus’, the author had asserted that (possibly paraphrasing Browne’s letter to Airy), ‘when the long-expected hour arrived, they were cool and collected, and found it hard to believe that the real transit was not merely model practice’.12 In fact, Airy had gleaned a different impression from the telegrams and reports of the observations that had been flowing in to Greenwich since the day of the transit. After receiving a batch of letters from Egypt and Hawaii, Airy contacted De La Rue, telling him ‘[the letters] impress upon me the feeling that very much will depend, for the final result, on the plain photographs [as opposed to the Janssen plates or telescopic observations] for the course of Venus across the sun … we must take steps without delay for measuring the photographs’.13 Airy wanted to test De La Rue’s rotating micrometer.14 The instrument had been designed by De La Rue to measure the circumference of the sun and the moon by tracing an arc of the edge of the image. Part of De La Rue’s plan for the transit photography included using this instrument, or a similar kind of rotating micrometer to find the centres of Venus and the sun from circumference measures. But after a ‘cool examination’ of the instrument, Airy decided it was more complicated than was necessary, returned it to De La Rue, and proceeded to construct his own measuring device. Instrument design was an area in which Airy had a long record of success. He had redesigned many of the instruments at Greenwich, such as the transit circle mentioned in Chapter 2. Airy’s design style, as historians have pointed out, tended towards simplicity and a focus on reducing the possibility of instrumental error.15 Reflecting this style, Airy’s ‘microscopic beam-compass micrometer’ was simpler, sturdier, and had fewer moving parts than did De La Rue’s instrument. But, as the name implies, the beam-compass micrometer only measured along a straight line in one direction.16 This was in direct contradiction to the advice of not only De La Rue but also Lewis Rutherfurd, who had cautioned

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that ‘no reliance should be placed for precision upon the apparent outline of the sun at any isolated point’.17 It was also the first independent decision made by Airy with regard to photography, and it is a sign of the much smaller role that De La Rue would play in this phase of the programme. His guidance would be almost entirely absent while the photographs were being measured and analysed. It is not clear whether this was his decision or Airy’s. Around the same time, De La Rue seems to have been making a general retreat from astronomy. In 1873, he had left his private astronomical practice at Kew, the Kew photoheliograph had been transferred to Greenwich, and the rest of his instruments were donated to the new Oxford University Observatory.18 Meanwhile, the debate over transit photographic methods (long-focus versus short-focus) continued to simmer, fuelled in part by an exchange in the Monthly Notices of the Royal Astronomical Society between Proctor and Christie and Abney (De La Rue had no comment). In April 1875, Proctor again raised the issue of how the scale of the photographs taken by the short-focus method was going to be determined.19 It was crucial that the measures of inches or millimetres taken from the images were accurately translated into seconds of arc. As described in Chapter 2, in the long-focus method the scale was to be found by measuring the exact focal length of the instrument, which would have been carefully made at each station using metal rods and jaw micrometers. The shortfocus plan was to calculate scale from measures taken from the photographs themselves by comparing the sizes of the objects (the angular radii of Venus and the sun, and the distance between their centres) in the photographs to the values of the same given in the ephemeris. Proctor rekindled the debate by reiterating his agreement with the Americans, the French and Lord Lindsay, who ‘after many experiments and long enquiry’ had come to the conclusion that measures of diameters could not be relied on for scale. In particular, Proctor raised the question of how irradiation would affect the apparent diameters of the sun and Venus in the photographs.20 Lindsay and Gill’s experiments had demonstrated the problem of ‘photographic irradiation’ by showing that brighter objects leave a larger photographic image than dimmer objects of the same size.21 They had thus concluded that this would make taking the scale from the photographs themselves impossible, and it was one of the reasons for their selection of the long-focus method. When these results were published, in June 1872, they received no response from Greenwich. But when the issue was raised again by Proctor in 1875, Abney argued against Lindsay’s conclusions about the causes of photographic irradiation. Apparently Abney had been performing his own studies of photographic irradiation, making use of a photoheliograph on loan to the Royal Engineers and of an instrument he invented called a ‘diaphanometer’. Lindsay had asserted that irradiation was caused by the photographic enlarging lens. Abney, on the other hand, believed

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that the cause lay with the wet-collodion photosensitive emulsions – that it was the result of a ‘spreading’ of chemical activity – and he claimed that it would not be an issue in his new ‘dry’ process: We are also told … that irradiation is a great drawback to our system. I think the effect of irradiation has been vastly overrated … The irradiation in the plates we use is reduced to a minimum, as the albuminate of silver which fastens the minute particles of iodide and bromide of silver together is nearly of the same specific gravity as that of the two latter. Experiment after experiment has shown to me that irradiation proper is really due to a reflexion from these minute particles, and if we connect them, forming nearly a continuous mass of the same specific gravity, it must be materially reduced, and perhaps eliminated.22

Furthermore, as Christie stressed in his defence of the short-focus method, determining the long-focus scale by direct measurement had its own problems, in particular that the ‘distance of the photographic plate from the optical centre of the forty feet lens must be determined with a probable error not exceeding 1/9000th part, or 1/18th of an inch’.23 In contrast to Abney, Christie did acknowledge that irradiation might make an imprint on the images, but he had a plan to correct for it. As irradiation made bright objects appear larger, the general effect of photographic irradiation, everyone agreed, would make the diameter of the sun larger and that of Venus (on the face of the sun) smaller. Christie therefore argued that the effect, in the end, would cancel itself out: irradiation will increase the sun’s diameter and decrease that of Venus to the same extent. So if the sum of the diameters of Venus and the sun was taken as the basis of the measure for scale, then any irradiation distortion would be removed. He further proposed to test the effect of irradiation using the ‘De La Rue scale’.24 This scale of equal parts for measuring the optical distortion could also have been used for irradiation investigation, since it was made of segments of metal plating alternating with open space through which sunlight was shone from reflecting plates behind. Perhaps based on these tests, as early as August 1875 Airy had drawn up a plan to determine the ‘constant of irradiation’, a value which would be subtracted from the measure of the diameter of the sun and added to the measure of the diameter of Venus.25 The expeditions began to assemble back at Greenwich in the summer of 1875. The chiefs of each station were expected to remain there for at least six months. With the assistance of two computers, their task was to produce the latitude, longitude and observation times for their stations. And while all this was proceeding Charles Burton, a Royal Engineer assigned to help the calculations at Greenwich, began with the analysis of the photographic plates (see Figures 13 and 14 above). Burton’s photographic work fell into three phases. First, the optical distortion of each photoheliograph was to be determined by measuring photographs of the scale of equal parts. Second, the scale of the images had to

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be measured, including, if necessary, accounting for effects of irradiation. And finally, the measure of the distance between the centres of the sun and Venus would be taken with Airy’s beam-compass micrometer. The first two parts were expected to finish by December 1875, but Burton would still be at it in April 1876. Meanwhile, Tupman began to unravel the observer reports and the new issue of the non-appearance of the black drop effect.

The Mist of Words As the chief of operations under Airy, George Tupman would play a central role in the reduction and publication phase of the enterprise. His return from Hawaii had been delayed by illness; he had contracted scarlet fever on a train from San Francisco to Chicago. Tupman’s health would remain poor for the next few years. Airy had an organized list of work to be done waiting for Tupman’s return. The list included calculating longitudes from lunar observations, the longitudes based on chronometric measures, the latitudes based on stellar transits, and the local sidereal time (from clock time or solar time) of every observation, double image measure and photograph of the transit. He was also expected to write up the histories of the expeditions, examine the state of the instruments, return the spare ‘military and other stores’, and settle ‘financial matters’ with the rest of the staff. ‘I in particular shall be very glad to be relieved by you in the superintendence of the Transit of Venus Work’, Airy told him, ‘it … is too much for me and I am suffering from it’.26 Tupman arrived at Greenwich after his long journey in late July 1875. Now back at the observatory and sifting through the observation reports, it was time to assess the success of the model training and contact method. The observers’ letters and reports had suggested to Airy that an exact moment of contact had been more difficult to pinpoint than had been expected. With all the reports together it was becoming clear that, despite the model training, observers were generally unsure as to when ‘contact’ should have been called. There were two problems in particular. First, the black drop and its phases, which had been consistently observed in the model, were only reported by about half of the observers. Second, many observers also described a new phenomenon that had not been represented in the model at all: a halo or thread of light around Venus, which was thought to be caused by the planet’s atmosphere.27 The halo was thin but bright, and some observers reported that it interfered with their ability to discern the moment of contact. According to Tupman’s first report on the matter to Airy, ‘The differences in the estimation of the moments of internal contact are caused chiefly by the disturbing influence of the atmosphere of Venus’.28 To Airy’s annoyance, although it may not have mattered, the ring of light could have been anticipated. Some of the eighteenth-century reports referred to it, and

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there had been a suggestion that the model should be redesigned to include an artificial Venusian atmosphere.29 Not only had the model produced a black drop that many did not see, but it also seems to have lacked an important feature. The hope had been to get observers to agree on specific phases of the drop formation, and yet they had not even agreed on whether a drop effect had existed at all. There was a deepening sense of having misapprehended the nature of the contact phenomenon. As Tupman told Airy in late July 1875, ‘It is time the term “Black Drop” was abandoned’.30 Somewhere along the way during the preparations, the ‘black drop’ had morphed from an eighteenth-century observer’s description into a something treated as real and definite. It had become, as Henry Russell of the Sydney Observatory put it, a ‘dependable phenomenon’.31 As Richard Proctor suggested, the black drop effect had, prior to the transit of 1874, ‘reached quasi-mythical status’.32 As the general consensus grew that ‘none of the skilled observers, who, in 1874, observed the internal contacts with good instruments, saw the so-called black-drop phenomenon’, Edward Stone defended his earlier work, which had given so much emphasis to the black drop, with a simple but fundamental point: ‘black drop’ had always been merely a metaphor for some kind of slowly changing events at contact, and as such it was irrelevant whether or not observers literally reported a ‘black drop’: Nothing whatever depends upon the phrase ‘black drop’ or ‘black drop phenomenon.’ This is merely the way in which one observer, in 1769, thought proper to describe the lingering nature of the contact, which is the cause of the only systematic error to be feared … Whether the observer prefers to speak of the disturbance of the apparent limb of the Sun near the point of contact, as an ‘ombre’, a ‘black-drop’, a ‘ligament’ a ‘thread’ or merely to assert generally that ‘the contact was gradually established’ is a point of very little importance. The important point … is the sensible time over which the contact extends …33

What mattered, Stone stressed, was that all observers saw the phenomenon of contact occur over a certain period of time, not that the terms in which those timings were couched varied or even contradicted. According to Tupman’s initial estimates, that period of time – the real differences between observers side-byside – was as long as twenty or thirty seconds.34 And, despite what Stone said, Tupman’s only option for bringing them into closer alignment (and thus reduce their probable error) would require liberal ‘interpretation’ of the descriptions of contact given by observers. For example, if one observer had called ‘contact’ at 6h. 11m. 15s., and his neighbour had described the formation of a ‘haze’ at 6h. 11m. 18s., but called contact at 6h. 11m. 25s., Tupman would have to justify taking the second observer’s description of the ‘haze’ as contact. According to Stone, that was fine. Observers who had stated that they saw no black drop effect had made such statements because of their ‘preconceived ideas

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of the nature of the phenomenon’, not because they had actually observed something very different from those who had reported that they did see the black drop effect. But of course the primary purpose of the model training programme had been exactly that: to build up a shared preconceived idea about contact. During the preparations for the transit, with all of the training directed at signalling ‘the formation of the drop and the formation of the clear circle’, expectations for what was to be seen were being reinforced.35 The British observers had not only been expecting the black drop, they had been relying on it. What went wrong? Possibly, as Stone was arguing, observers had learned to interpret the model contact in a uniform manner, but this did not help them because they had not learned to interpret the comparison between model contact and real contact in a uniform manner. Or, possibly, Stone was wrong and contact really did appear differently from one location to another, and from one observer to another. It is impossible to say what had happened, or indeed whether the observation reports reflected reactions to model-world comparisons, to the phenomenon itself or to something else entirely. The fleeting and subtle nature of contact that was frustrating Tupman’s analysis of the 1874 data also, from a historical perspective, frustrates our understanding of why – and in fact whether – the observations of contact had failed. ‘The essential facts’, Stone worried, ‘are in this case, as in too many other cases of the kind, becoming veiled in a mist of words’.36 There was a sense of bottomless uncertainty about what the observation language of each report should be taken to actually mean. Indeed, as would become clear during preparations for the transit of 1882, even to an observer himself, it was not possible to say exactly what he had meant in his observation reports from 1874.37 To Tupman, that mist seemed impenetrable. Analysis of the observer reports was put on hold for a few years, ostensibly while the longitude and time data was being calculated, but also in the hope that the photographic data would produce more solid and less problematic results. Roughly two years would go by before the problem of interpreting the observer reports was picked up again. In the meantime, new problems with the photographic method would be uncovered. The programme’s financial situation would also take a turn for the worse.

Financial Crisis Tupman’s contract at Greenwich was due to expire in March 1876, but the work was nowhere near finished. By that time, the other station chiefs had completed their longitude work and been dismissed. Only Burton and Tupman were left to deal with analysing the data and drawing up the reports. So Airy asked the Admiralty to extend Tupman’s contract for another year. The reply came as a shock: a letter forwarded from the Treasury charged that ‘the total expenditure

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of the service which has been charged … amounts to over £40,000’. The programme budget had been set at £15,500. Airy, taken by surprise, was requested to furnish a ‘full explanation of the very large excesses of expenditure’.38 Only a few months earlier, apparently entirely unaware of any financial problems, Airy had confidently requested that Tupman’s salary be increased by £100 to £500 per annum, in acknowledgement of his central role in the project.39 In fact it may have been this haggling over employee salaries (the Admiralty had countered that Tupman should instead get a lump sum of £500 at the end of the project) that initiated the Treasury’s assessment of the financial situation. In his reply, Airy argued that he was only directly responsible for a small part of the overall expenditure, and that the rest had been controlled by the Admiralty. He listed the cost of the astronomical instruments and accessories, which, including photography, came to £10,579. The estimated cost had been only £5,880. In explaining the overdraft, he cited an ‘addition of late expenses’, in particular the Janssen apparatus, extra eyepiece micrometers, and especially the framed instrument huts, for which ‘the expense exceeded all anticipation’. Having thus taken responsibility for £5,000 of the extra expense, Airy claimed ‘no distinct information on the remainder’. The travelling costs, which amounted to £10,390 had not been included in any of the original estimates, and Airy says he had ‘no knowledge or control’ over that or any other part of the programme beyond the instruments and their outfitting.40 Neither Greenwich nor the Admiralty, it seems, were ultimately accountable for the programme’s finances. Each blamed the other for the excessive spending. In a similar way, the oceanographic expedition of the Challenger at around this time would run into serious financial trouble during the analysis and publication of its results. As it seems to have been with the transit programme, the initial budget had provided seriously insufficient funding for the analysis and publication of results. In the end, the voyage of the Challenger would cost the Treasury £200,000. According to A. L. Rice, ‘so shocked was the Treasury at its unintended generosity, that it was to be several decades before it again became involved in a comparably expensive scientific undertaking’.41 The financial black hole in the transit budget also illustrates the difficulty the Treasury had in enforcing accountability at the level of scientific enterprise. According to MacLeod, an inability to resolve financial accountability on both sides – that is for science workers to appreciate the importance of accountability, and for the treasury to enforce methods supporting it – was one of the major roadblocks to the endowment of science at the time.42 Such problems are underlined by the fact that Airy, who had an impeccable reputation for financial responsibility, also ran into such problems. In this context it is especially interesting that when the Admiralty refused to participate in the transit of 1882, the Treasury decided to provide financial backing directly.43

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Airy managed to have Tupman’s contract extended until September of 1877, at which point all funding for the 1874 transit of Venus programme was to cease.44 The programme seemed secure for another year, but it was clearly operating under financial pressures. Costs were now being very closely watched by Airy, who seemed to have sole responsibility for the accounting. Decisions about which lines of investigation to pursue were often made on financial grounds. The labour-cost of each particular step in the reductions was known. For example, the cost of determining the distortion of the photoheliographs had reached, by 2 March 1876, £9 15 s. 6 d., and a mistake that Burton had made early on meant that £8 worth of this labour was going to have to be redone.45 Even the colonial observatories were to be charged for the cost of reducing their portion of the data. Airy wanted £50 from the Melbourne, Sydney and New Zealand governments to handle their photographic data.46 ‘Much depends on a delicate discrimination of the various phases of the proximate contact of the limbs of sun and planet’, Airy told R. J. Ellersy, the government astronomer in Melbourne. ‘We are now engaged on the photographs, but they seem likely to give us trouble and uncertainty.’ The colonial astronomers, though willing to pay, were ‘not hopeful that the result would be good’.47 By June 1876, a year after the calculations had begun, it was quite clear that the programme was in trouble. There was little confidence in the telescopic observations, the photographic programme had not yet progressed beyond the initial phase of optical distortion measurement, and there were few resources – only two full-time positions – available to help solve these problems. Yet, unlike the public scrutiny that the transit preparations underwent, the precarious state of the transit calculations seems not to have been widely known. Even as Burton was struggling to make sense of the photographic data, Airy was showing off prints of the transit of Venus photographs to Queen Victoria.48 A full set of instruments and cabins had been loaned to the new South Kensington Museum and, at the grand opening of the Special Loan Collection in 1876, a complete recreation of one of the observation stations was on display. At the same time, however, neither the politicians nor the press seemed to have any knowledge or interest in the impending failure of their national scientific endeavour. The Admiralty, however, wanted a publication.49 That was a sensitive issue. In reply to a query about when results could be expected, Christie, Airy’s first assistant, who was now often responding in place of Airy, focused on the positive, emphasizing the fact that ‘the great mass of calculations required’ for longitude had been nearly finished. Barring unexpected difficulties, Christie supposed that in another three months all of the preliminary calculations would be done. At that point, Tupman could begin the discussion of results, which Christie described as ‘a subject requiring very careful consideration, though no very great labour is involved … [the] discussion involves so many delicate considerations

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…’. And this, the Admiralty was reminded, was only the first step in the ultimate plan to combine all of the observations made worldwide: The result thus obtained for the Sun’s distance can however only be regarded as provisional, as other nations have cooperated in the Enterprise, and it may be necessary to wait several years before their results are known. On this point we have very little information, and that chiefly negative; it seems probable, however, that the results of the British Observations will be made public before those of any other nation, though it may, perhaps, not be desirable to state this opinion publicly.50

The suggestion that the British programme was progressing faster than the other nations seems to have had no real basis. This would not be the last time that the Admiralty would be given a highly glossed report of the programme’s progress. Christie had told the Admiralty that results would be ready for publication by June 1877. In April 1877, the issue of transit results was raised for the first time in parliament. The MPs, who by this point may have forgotten entirely about the transit, were reminded of it by Hugh Childers, who had been First Lord of the Admiralty when the programme had initially been proposed.51 Greenwich was soon made aware that there were new pressures for publication.52 Meanwhile, work on the photographic material had inched along throughout 1876 and the first half of 1877, and still the scale and the distortion, which according to Airy would require upwards of 6,000 measures, were not yet determined. In the process, however, other problems had been discovered, such as the fact that at Kerguelen the photoheliograph had been ‘hopelessly out of focus’ on the day of the transit.53 And Stephen Perry, chief of the Kerguelen expedition, apparently had also failed to properly superintend the longitude work.54 It now seemed sure that the photographic data would not be ready for another year, so it was decided to publish initial results based only on the telescopic data. Tupman’s attention thus returned to the ‘delicate’ analysis of the observers’ language.

‘Casting’ Phases and ‘Doctoring’ Results The problem, Tupman told Airy in June 1877, as he began to organize parliament’s report, was that ‘any translation of the language employed … would give a result ranging within the limits of 8˝.65 to 8˝.85’. This range (152m km / 94.5m mi to 148m km / 92m mi) was even wider than the currently accepted values for parallax, making the results essentially useless.55 In search of some kind of rigour to apply to the interpretative work, Tupman defined a system based on sets of ‘phases of contact’ that he tried to identify in each description, and aligned the reports according to these phases. There were three phases each for ingress (α, β and γ) and egress (δ, ζ and η), roughly corresponding to beginning, middle and end of contact. Then, observations of α at an ingress accelerated station would be compared with α at an ingress retarded station, and likewise β, γ and the rest

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of the phases. Focusing on these phases, Tupman could ignore to some extent the language of the observers and work instead, as Stone had suggested, on the intervals of time between the successive timings of each observer. It was agreed between Airy and Tupman that when two phenomena are recorded at similar intervals of time at two stations, this can be taken as strong evidence that the observers were referring to the same phenomenon even when the descriptive language differs (such as when one saw a black drop and when one did not).56 Still, the identification and sorting of phases was an uncomfortable process. It was known by that time that any reasonable value for the solar parallax lay somewhere between 8˝.70 (151m km / 94m mi) and 8˝.9 (147m km / 92m mi, with most methods converging around 8˝.8 (149.5m km / 92.8m mi). A target ‘good’ result was therefore evident, and could be pursued through different interpretations. How should Tupman conduct his analysis in such a way that got them acceptable results, but did not do so in a way that would be considered unacceptable or manipulative? The case of the Rodriguez data made the problem clear. The difference of the distance of centres for Rodriguez and Egypt was unsatisfactory, leading to an especially small value for parallax. This could be improved if the Rodriguez timing of contact was altered by about 30 seconds. At first it was thought that perhaps the pocket watch that had been used to time contacts (when a chronometer or transit clock should have been used) had not been properly measured for an error rate, but no problems could be found with the instrument or its rating. What remained then was to use the ‘phases’ system to extract the desired result. Airy finally instructed Tupman: Try whether you can force the Rodriguez Egresses into agreement, (it can hardly be doubted that they can with fairness be made to agree). I will take care to explain things at the end that there can be no imputation of coaxing.57

Airy had high hopes for Tupman’s phases method, and expected that it would become the ‘standard’ for transit reductions.58 Tupman, on the other hand, was sceptical of his own work, and wanted an independent astronomer to perform a second pass on the data.59 Throughout this history of the transit programme so far, the suppression or diminishment of personal judgement or reason has emerged as a major theme, an issue which Airy and Tupman were especially concerned with. It is interesting to come across, in the calculation stage, a procedure for bringing reasoning back into the result. The weighting of the merit of observations, though completely common at the time, nevertheless modifies our picture so far of the transit staff ’s conception of impersonality with respect to good practices of observation. Judgement was in fact given a very important role, but a role that was, in the formulation of the results, isolated from the observational data. Judgement took the form of a single numerical value that could be examined and debated separate from the data itself.

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Just before publication, one last piece of analysis was added to the report. It will be recalled from Chapter 1 that Richard Proctor had initiated a protracted debate over whether Britain should use the method of durations (Halley’s method) or the method of difference of times of ingress and egress (Delisle’s method). Since one station relatively far north (Rodriguez) and one station relatively far south (Kerguelen) did see the whole transit, it was possible to make a measure of parallax by the method of durations. This came as an afterthought and was done only to pre-empt any criticism by Proctor. Airy wrote to Tupman on the eve of publishing the report: I have forgotten to mention that materials (poor ones, I fear) exist for inferring the parallax from the comparison of observed duration at Rodriguez with observed duration at Kerguelen. It will be five minutes calculation, pray work it out. Else what will Mr Proctor say?60

The focus of the programme remained, as it had from the beginning, on Delisle’s method. It is puzzling that Proctor seems never to have strongly criticized the results of the 1874 enterprise. After such vicious public attacks on Airy’s plans during the preparations, one would think Proctor would be ready to pounce. On the other hand, it was not as if he could point to the American system, which he had so strenuously advocated, as clearly on the way to getting better results. The first official report was published in July 1877. Combination of the results for ingress, giving the most weight to observations corresponding to the phase β, produced a parallax value of 8˝.739 (149.6m km / 92.9m mi). Egress, where the phase ζ seemed most reliable, produced a parallax of 8˝.847 (148.6m km / 92.3m mi). These two were combined, with much more weight being given to ingress, to produce the final value of 8˝.760 ± 0˝.122 (150.1m km / 93.2m mi ± 4.1m km / 2.5m mi).61 The probable error, spanning the entire range of currently accepted parallax values, was far larger that had been hoped. But at least there was result. The main purpose of this report seems to have been to satisfy the Admiralty and parliament, who seem to have been unaware of any shortcomings in the result. And, as Christie had promised, it was the first transit report to be published (though a French astronomer had announced a preliminary result for parallax in the spring of 1875). Airy made sure the Admiralty did not miss that point: We are the first of nations in preparing these results, and I am anxious to secure incontestably this precedence. We have introduced some new considerations … which may probably influence the proceedings of other nations. And we have obtained results, in some degree unexpected, which both on their own sake and for the impression they may make on others, it is highly desirable to disseminate as soon as practicable.62

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In the days before the report was finished, Airy had been extremely anxious to get the publication out as soon as possible, though the reason for the rush is unclear. It may have been that he knew a first volume of the American results was imminent. The performance of Greenwich in relation to other nations was a subject Airy often brought up in the last years of the transit programme, especially in his correspondence with the Admiralty. At this stage, Airy was not a man to whom, as some historians have claimed, patriotic issues were irrelevant. At the very least, he understood how they might be used to influence the government’s thinking.63 Among the astronomical community, however, it was clear that the results were disappointing. Soon after the publication appeared, Tupman asked for second opinions on his interpretation of the data. Christie and Gill separately examined the reports and came up with parallax values around 8˝.74.64 But Stone’s results were not in agreement. Disagreeing with Tupman on many points of ‘translation’, Stone rejected Tupman’s ‘phases’ system and instead chose to focus only on when observers seemed to mark ingress or egress ‘complete’. After a lengthy justification of his own interpretations, Stone presented a parallax of 8˝.884 ± 0.123 (148m km / 92m mi ± 4m km / 2.5m mi), and argued that no ‘rational’ interpretation of the reports could produce a parallax lower that 8˝.84.65 In any case, both Stone’s and Tupman’s results were within each other’s equally large range of probable error. In a final recalculation of parallax, published in June 1878, Tupman was openly critical of his system of ‘casting phases’. In a concession to Stone, he pointed out certain cases where ‘the attempt to fasten these phases … upon everybody’s observations led to very erroneous results’. And he admitted that ‘any selection of times made after an investigation of the effects of parallax, such as that I have now made, will always expose the result to the suspicion of having been “doctored”’.66 In this final parallax calculation, Tupman also used the widest-yet selection of observations, including those of C. Ragoonatha Chary in Madras, the Mexican observations in Japan, the German observations at Luxor, many private observations from Australia, the report of Mahmoud Bey at the Khedive’s Observatory (using a provisional longitude supplied by Browne), and two other women besides Emily Newton: Mrs Campbell (at a private station in Thebes) and Miss Pogson (at Madras). His final results were, for ingress 8˝.845, and for egress 8˝.846. ‘Although the above results of Ingress and Egress present such an unexpected agreement’, he added, ‘it cannot be said that the mean 8˝.8455 is entitled to much confidence, since all the observations would be fairly well satisfied by any mean solar parallax between 8˝.82 and 8˝.88’ (149.1m km / 92.6m mi to 148.1m km / 92.6m mi).67 That remaining range of values – expressing an uncertainty in the sun’s distance of well over half a million miles – captures

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in a nutshell the fatal shortcoming of the 1874 results from observations of contact. And that range, it should be pointed out, is from the most generous treatment of the data from the British programme. In this light, the results from 1761 and 1769 also began to look different. It was inconceivable that the results from the eighteenth century were more valuable than those of 1874, yet if Stone’s 1868 reassessment of the eighteenth-century data was correct, this would be the case. Tupman concluded his report with an argument against any such claims. He suggested that Stone’s work on the eighteenth-century data was equally – if not more – open to accusations of ‘doctoring’, and that Stone had entirely overestimated how well the eighteenth-century data agreed: ‘The probable error of [Green and Cook’s] contacts, instead of being 3s as Mr. Stone thought nine or ten years ago, was more likely 20s or 30s …’.68 Whatever doubts there were about the transit of Venus method at the start of the preparations for 1874, it had been widely assumed that, at the very least, the modern attempt would produce more valuable data than that of a century ago. There was now the real possibility of that not turning out to be true.

Figure 16. ‘Success of Stations, as reported in Telegrams etc.’ From G. Tupman, in The Engineer, 12 April 1875, p. 224.

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Deciding that Photography had Failed While Tupman had been at work on the observation reports, Burton had completed one pass on the photographic data and made a first attempt at calculating parallax. The result, at 8˝.2 (160m km / 99m mi), was dismal. No one knew what had gone wrong. At first, Airy suspected that it had to do with some kind of personal equation for the microscopic beam-compass measurements. Tupman thus made his own series of measures, and Burton made a second pass as well. On comparison, a significant and apparently systematic difference between Tupman’s and Burton’s measures became apparent: Burton’s second series produced 8˝.08 (162m km / 101m mi) and Tupman’s produced 8˝.25 (159m km / 99m mi). All three of the results only highlighted the fact that somewhere there was a much more serious source of error. All three measures produced what seemed to be a ridiculously long distance to the sun – around 100 million miles. At this point Airy began to take a more direct role in the photographic work, personally investigating a variety of possible causes. One of his first lines of pursuit was atmospheric distortion, which might cause the sun to appear ellipsoid rather than circular. He also suspected that the scale calculated from the ratio of the diameters of Venus and the sun on the photographs was incorrect or inconsistent. And he now seriously doubted their earlier assumption that the force of ‘photographic irradiation’ was constant. ‘To obtain a scale, I had supposed that we might assume some uniformity of irradiation. The Sydney photographs have destroyed that idea.’69 It is unclear what exactly the Sydney photographs had shown, but Airy now worried that either photographic irradiation was stronger at the centre of the sun than at its edge, or that its strength varied according to the altitude and atmospheric effects at each station. It may have been possible to identify and correct for any of these problems, but that would require much more time and research. The financial climate was not a good one for openended investigation. Airy had recently applied to the Treasury for funds to cover more computers, but this had been denied. Tupman’s contract expired at the end of September. For a third time, Airy approached the Admiralty for an extension, arguing that Tupman was at a crucial point with the photographic data where ‘delicate considerations arise’ and that the termination of his contract would result in ‘delays discreditable (in their degree) to the nation’.70 The Treasury once again authorized an extension for Tupman until April 1878, but with a salary reduced to the level of second assistant. What was needed was time to explore the operation of the photoheliograph more fully and to make some further photographic experiments, but what they now had was at most a few months to get to the bottom of the problem. December and January thus became crucial months for the success or failure of

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the photographic plan. While Airy searched for systematic problems in everything from personality to the photographic film (at one point Airy wondered if it could change thickness day by day) to irradiation, Christie and Tupman had come to the conclusion that the images simply were not sharp enough to be measured with Airy’s beam-compass micrometer, or perhaps at all. Tupman had very little hope for improving the photographic results: ‘I take the view that with such materials as these photographs it is surprising to get as accurate a parallax as 8˝.2!’71 Christie labelled the cause ‘atmospheric disturbance’, explaining to Airy that ‘the irregularities of the limb from atmospheric disturbance amount to 5˝ or 6˝ on the average and one observer might take the top and the other the bottom of a wavy line …’. He was therefore ‘not in the least surprised’ at the difficulties they were having.72 It was clear to Christie and Tupman that De La Rue’s radial micrometer, designed to average out the irregularities of the solar limb, offered at least a chance of better results. But Airy was strangely resistant to the idea, and stubbornly maintained that any benefits of De La Rue’s complicated micrometer were outweighed by the likelihood of instrumental error. At first, he was even opposed to running trials with De La Rue’s micrometer, claiming his ‘stout beam-compass’ was the proper instrument for the task. We have a very simple fact to [uncover] namely the intervals between four points in a straight line, and if the most ordinary care is taken … by means of the wire-apparatus, and if the wire-apparatus is correct, the immunity from error here is remarkable. I assume that Capt. Tupman has, during the course of the work, looked to the general accuracy of the above-mentioned apparatus. And the measuring apparatus is the most simple that can be conceived. I see but two grounds of error: culpable negligence, or ocular personal equation … I am not disposed to spend anything on the more complicated operations which you propose.73

Later on he would reiterate his opinion that ‘Our terrible difficulty is not instrumental; it is the systematic discordance between Tupman and Burton’, though at other times he would blame irradiation, the scale, the shape of the sun, or the film.74 In an attempt to persuade Airy, Christie spelled out the benefits of the radial micrometer once again: It seems to me, looking at the irregularities of the limbs of the Sun & Venus on the photographs, that we must treat the photograph itself as fallible, and that no repetition of measuring any one point of the limb in one photograph will ever get rid of this error. But possibly by taking an average of the whole limb of the Sun and the whole limb of Venus, the error from this irregularity will be nearly eliminated. The present mode of measurement could hardly be improved provided it were sufficient to measure the distances of the four points on the photographs, but the case seems to me to be different when it is required to measure the true distances of the points on the Sun & Venus, of which the photograph gives a fallible representation. As the method used

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The Transit of Venus has given such unsatisfactory results I merely suggest a new method of measurement as an experiment in the hope that some light may be thrown on the subject.75

Airy eventually allowed De La Rue to bring his instrument for trials in midJanuary 1878. The results seemed encouraging: from measures of one plate the discordance between Tupman and Christie equalled 0˝.12, roughly half that of the prior measures of Burton and Tupman.76 An undated page of calculations from around the same time seemed to give more promising results: 8˝.5 for a comparison of Hawaii and Rodriguez photographs, and 8˝.6 for Hawaii and Kerguelen.77 But still the parallax value was too low to be considered useful. Airy was at a loss: ‘I am really afraid to suggest any thing about the T.o.V. photographs. Every step now is one of experiment’.78 His final conclusion seems to have been that irradiation was relatively constant for the plates of each station, but that it varied from station to station due to the atmosphere and conditions, leading to an incorrect scale calculation and the low parallax.79 It might have been possible to work out some kind of irradiation constant for each station that would resolve the error. But morale was low, money and time were short, and the conclusive account of the enterprise remained to be written. So it was decided to concede a failure in the photographic programme and abandon any attempts to turn it around. All that now remained was to make the failure publicly known, which Tupman did in a Monthly Notices article in June 1878. Though not venturing to suggest a concrete reason for the low parallax value, the Greenwich group admitted in the article that, in the debate over the long-focus and shortfocus methods, they had been wrong: ‘These discordances support the decision of the American Commission that the photographic diameter of the Sun cannot be relied on when accuracy is required’.80

The Official Publication and the Retirement of the Astronomer Royal Tupman’s latest extension was due to expire at the end of March 1878, and the Treasury had warned Airy that no more funding for the transit would be sanctioned after that date, even after Airy argued for more time. Yet work on the final publication, including observer reports, longitude determinations, expedition narratives, and maps and drawings, had not been started. And Tupman had hoped to continue the ‘severe and critical examination of the terms in which the observers have given their observations’, including a consideration of Stone’s independent result. But the Treasury stuck to its position. Unable to leave the work unfinished, Tupman agreed to continue ‘the perfectioning of the work’ without pay, and Airy offered to ‘defray the accompanying expense of hired assistants’.81 This would be the situation for the next two years.

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These years were almost entirely devoted to compiling and printing the report. In fact the 1881 report does not give any resulting value for parallax. It had been proposed in 1875 that, in addition to following Airy’s proposal for the form of the reports, each country should refrain from producing an independent value for solar parallax. As it had been put in the preface to the American report of 1880, ‘Publications of separate results for the solar parallax from the observations of the Transit of Venus of 1874 are, so far as practicable, to be avoided as detrimental to the interests of science’.82 What the British report does contain are lengthy and detailed descriptions of the expeditions, the instruments and their histories, the procedures of observing, longitude and latitude work, and finally the equations of distances of centres for each separate observation. Photography is dealt with in a short appendix. The operation of the photoheliograph, the calculation of distortion from the De La Rue Scale, the beam-compass micrometer and the method of measuring the photographs are all briefly described. As for the Janssen plate pictures, this is all that is said: ‘The ardour of the Observers had been much cooled by the apparent general failure of the photographic principle, and they were unwilling to spend further time on these reductions’.83 As for the cause of the failure, Airy, in his final statement on the matter, repeated what Tupman had concluded in his 1878 Monthly Notices article: ‘however well the Sun’s limb on the photograph appeared to the naked eye to be defined, yet on applying to it a microscope it became indistinct and untraceable, and when the sharp wire of the micrometer was placed on it, it entirely disappeared’. The misapprehension of the black drop effect was not directly addressed, but the failure of the model to represent contacts realistically was frankly described: ‘As regards the instant of internal contact, the appearances of the model bore no resemblance to the phenomena of the actual transit of Venus’.84 In 1879, the question of transit results came up in parliament for the last time, in the context of a debate about the accountability of government-funded science projects. In a discussion of the naval supply estimates for the next year, one MP, E. J. Reed, was demanding that the House be given better information about the activities of the scientific branches of government. He complained that the published reports were useless to MPs, who could neither understand the results of the scientific programmes nor ‘trace their operations’.85 Another MP, Captain Pim, agreed. He passed out a copy of a report from the United States Secretary of the Navy, which, as he said, was ‘clear’ and ‘full’. It gave, ‘in a readable form’, all the information they wanted, and, surely, it would be no trouble on the part of the First Lord of the Admiralty to prepare a similar statement and lay it on the Table with the Votes, so that the hon. Members would be able to look into those matters, and take up those points, in which they felt an interest. They certainly ought not to

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The Transit of Venus have to wade through a mass of figures which were as vague and as ill put together as anything he had ever seen.86

But a summary of the military’s scientific works written up expressly for MPs would not materialize any time soon. Well into the 1880s, MPs were complaining to the Admiralty about the lack of clarity concerning the scientific departments to which the MPs were annually voting funds. In 1880 Reed would again bring up the question of scientific reports, claiming that ‘the House has no idea what the Hydrographic department, for example, is up to’.87 In 1886, in connection with a vote for £7,600 to the ‘Learned societies and Scientific Investigation’, someone objected on the grounds that a portion goes to supplying papers with weather reports, which are always wrong. Another MP brought up the oceanographic expedition, which itself was in financial trouble at that time. One MP, Dr Tanner, demanded to know ‘what is the great practical benefit’ of the expensive effort. So far as he could gather from the reports, ‘the principal result has been to find places at the bottom of the ocean most suitable for laying down cables’. Commander Bethel of the Admiralty pointed Tanner to the 30 ‘large volumes’ of Challenger log books, suggesting that ‘if the hon. Member will study these log books he will perfectly understand the object of the Expedition’. To this Tanner exasperatedly replied ‘I maintain that we should not be always asked to read these terrible volumes which are issued from time to time in connection with our scientific services’ and asked to be told ‘in a short and succinct form’ what the expense was for. At this point, Sir Herbert Maxwell of the Treasury stepped in, confirmed that submarine telegraphy was ‘the true origin of the Expedition – namely the great extension of the Sub-Marine Telegraph Service, and the immense development of telegraphic communication between the different parts of the world’. He then challenged anyone in the Committee to underrate the importance of that matter. Only as an afterthought did he also point out that there was ‘connected with this expedition … an immense development of biological science’. Apparently, however, the MPs had got it backwards, believing that the benefit to the telegraphy industry had been a by-product of some other more noble pursuit.88 Back to the discussion in 1879, Hugh Childers brought up the question of the ‘very large expenditure’ that had been granted for the transit of Venus programme, the results of which he believed were ‘of very great value indeed’ but had not been made public. Airy’s report for parliament in 1877 had made very little impact on parliament’s collective memory. As the wider context of the debate on this issue suggests, this was not unusual. In reply to these criticisms, the current First Lord made no mention of either the 1877 report or the financial and analytical problems that had nearly ground the programme to a halt. Instead, he rested the blame on Airy’s age:

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… the officer who is now in charge and at the head of the Observatory is a gentleman who is entitled to a great deal of consideration, for he had rendered very great services to the State, and it is not possible to press him in the same way as we would have pressed a younger man.89

In 1879 Airy was aged seventy-eight. The 1874 transit of Venus enterprise and his career as Astronomer Royal would draw to a close together. The Report on the Observations was sent to press in mid-July 1881. Just a month later, on 16 August 1881, Airy (‘wearied’, as his daughter would put it, by the ‘long-continued drag of the Transit of Venus work’) finally retired at the age of eighty-one.90 Christie was soon selected as his replacement. (Surprisingly, according to Otto Struve, Richard Proctor had been among those also being considered for the post.91) It turns out that when the Daily News had alleged in 1875 that Airy was immune to any ‘official reprehension’, there had been an element of truth in it.92 The programme had spent three times as much money as was budgeted for it, and it did not achieve its primary objective. Yet Airy, through publishing reports when the government asked for them (even if they were apparently never read), avoided any direct implications of failure. The clearest indication that the government was relatively satisfied with the 1874 enterprise would be its willingness to fund more expeditions in 1882 (although the Admiralty would refuse to be a part of it). For Airy, however, the 1874 transit was surely not the positive note on which he would have wished to end his forty-six-year career.

Outcomes and Results Beyond Greenwich Back in 1875, Airy had hoped that a ‘foreign astronomer’ would take up the task of combining all the world’s observations into one result, but that would never happen. Instead, the reports and calculations from each country trickled out separately over the next two decades. Lord Linsday’s expedition only published the results for the chronometric longitude determinations, though this in itself was an extensive assessment of the chronometric method of longitude. After the transit of Venus, David Gill had moved on to Ascension Island and to finding parallax by observations of Mars in ascension in 1877. ‘Seeking new pastures’, as Lindsay put it, Gill would never return to the heliometric or photographic data from the transit of Venus.93 As for the photographic results by the American long-focus method, in 1877 William Harkness, who was in charge of reducing the photographic data, had reported that the measurement of the photographs was complete and yielded ‘excellent results’. But the determination of longitude and time information for each station was still far from finished and no parallax value was then published. On the eve of the transit of Venus in 1882, the American results were still unclear. Although no final result was available, Harkness claimed to have

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achieved an accuracy one hundred times greater than that of the British. He also described how initially he had stumbled on ‘the same difficulty which had baffled the English’, the indistinct blur of the image under a microscope. But, as he explained, he soon realized that he had been using an ‘utterly preposterous’ power of magnification. When he reduced the power from 37.5 to 5.5 times the diameter of the sun, ‘all the difficulty vanished and the photographs yielded excellent results. The measurements made upon them seem free from both constant and systematic errors ….’94 However, it should be made clear that the issue of over-magnification was almost certainly not the primary problem with the British data; Tupman had stated in his Monthly Notices article of 1878 that an amplification power of only 5 or 6 diameters would bring out the blurriness of the limb.95 In any case, as later publications would make clear, there is no doubt that the long-focus method produced more accurate and less problematic results than had the short-focus method. Yet the American photographic programme was not completely successful. Harkness’s photographic results would never be published by the Transit Commission. By 1880 only the first two volumes of the transit report, dealing with the preparations and the longitude work, were published.96 According to the Secretary of the Commission, Simon Newcomb, a frustrating lack of financial support from the government resulted in the staff computers on the transit programme being fired and rehired three times, seriously delaying the work.97 Steve Dick has concluded that the reasons for the American failure to publish a result were primarily ‘bureaucratic’.98 Newcomb himself had lost confidence in the transit of Venus method and was sceptical of the value of the photographic data. But Harkness would continue working on the transit photographs, and he would be one of the most vocal supporters for its use in the transit of 1882. His final result, a combination of the data from 1874 and 1882, would appear in 1891.99 Russia’s results, consisting mostly of the longitude determinations of the Siberian stations (most of which had had cloudy weather for the transit), would also appear in 1891.100 Germany’s results would follow in 1895.101 Neither Germany nor Russia published data from their photographic programmes. In 1880, France published a result of 8˝.81 in the Comptes Rendus. The final volume of France’s series of transit publications, probably the most detailed and extensive of any programme, would be completed in 1885.102 Meanwhile, other avenues of research into the solar parallax were attracting more and more attention. Urbain Le Verrier had published a new system of astronomical constants, including solar parallax, based on gravitational theory. Gill’s heliometric measures of Mars in ascension in 1877 were highly regarded, as were the light-speed experiments that Simon Newcomb and Albert Michelson made in 1880–1.103 But the transit of 1882 was approaching fast. Amazingly, despite the disappointing results for 1874 and the many promising avenues of

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parallax research by other means, the chance to test the transit of Venus method one last time would prove to be strangely irresistible (see Epilogue). In 1888 William Harkness reported the value calculated from 1,475 photographs from both the transits of 1874 and 1882 as 8˝.847 ± 0.012 or 92,385,000 ± 125,000 miles.104 He later refined the final American result to 8˝.809 ± 0˝.0059 or 92,797,000 ± 59, 700 miles.105 In 1891, Russia produced a publication on the 1874 expedition, but no value for parallax was given and the focus was on the latitude and longitude measures of the twenty-one stations in northern Siberia.106 In 1895, Auwers published the fifth and final volume of the German series on transit heliometric results. The final parallax deduced from the two transits was reported as 8˝.890 ± 0.0216, a value acknowledged as likely to be much too high.107 French results for 1882 were announced in the Comptes Rendus of 11 December 1899. Considering only the visual observations of the ten expeditions sent by France to North and South America, the definitive result was 8˝.80.108 All of the transit of Venus stories from different nations would converge in 1896, at the Conferénce Internationale des Etoiles Fondamentales in Paris, when a new number for solar parallax was agreed upon by the United States, Britain, France and Germany, and then adopted internationally. The value adopted at the conference, 8˝.80, was that proposed by Simon Newcomb in The Elements of the Four Inner Planets and the Fundamental Constants of Astronomy (1895). Newcomb arrived at this value by making a supreme merger of all of the data from every relatively well-respected measure of solar parallax. The first step was to arrange all of the results into nine classifications of different methods of measuring parallax. He then took the mean of the results for that method. For example, the value given for the method of observations of contacts during the transits of Venus (8˝.794 ± 0.018) is not the value determined by any single programme but the mean of all of the results from 1761 to 1882. He then assigned a weight, ranging from 1 to 40, to each result. Harkness’s photographic method was given a weight of 2; the observations of contact of the transit of Venus received a weight of 3. At the top of the list, the Pulkovo determination of the constant of aberration was given a weight of 40.109 The Paris conference was a great success in terms of international cooperation on standard measures. The directors of the French, German, American and British Nautical Almanacs agreed to adopt the new value of 8˝.80 as of 1900. To make this upgrade in the almanacs would require a massive recalculation effort, and the Almanac Offices, according to Steve Dick, very rarely agreed to make such overhauls.110 Indeed Newcomb’s value would remain the standard for the almanacs until 1964. In the end, the eighteenth- and nineteenth-century transit programmes throughout the world all contributed in the same slight manner to the first international standard of solar parallax.

CONCLUSION

Figure 17. The back plate to the bound annual of Punch, 1874. Reproduced by permission of the Bodleian Library, University of Oxford.

Measurement in Late Victorian Science The predominant story of the physical sciences in the nineteenth century is about the success of quantification, and the successful extension of measuring instruments into new areas of enquiry. Quantification came to the forefront, supplementing the experimental method that emerged from the seventeenth century. This story is tied up with the standard story of the birth of physics, where during the period between 1750 and 1850 qualitative studies of chemistry, electricity and magnetism were replaced by quantitative studies made possible by new instrumentation. From the 1850s onwards this movement was accompanied by a whole new push for standardization of measurement. It was not only physics that saw rapid expansion in quantitative measurement. Social and human sciences were similarly affected. In the late 1860s, these disciplines began using new technologies to replace the role of descriptive observational language, for example the new range of recording instruments in physiology (such as the kymograph, myograph, cardiograph, thermograph and pneumograph).1 – 147 –

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In short, the nineteenth century witnessed an explosive growth in measurement across a wide range of scientific practices. Astronomy, of course, had for centuries been the model of what a science can achieve through precision measurement of the natural world. Historians have argued that the push for quantification in these new disciplines enabled them to catch up with the ‘classical’ quantitative sciences of astronomy, optics and mechanics.2 Here, then, is one of the strangest aspects of the transit of Venus enterprise: at the apex of positional astronomical measurement techniques, and at the height of a new quantification wave spreading throughout scientific practice in general, progress stalls at Greenwich. Greenwich, ruler of precision numerical measurement for 300 years, suddenly found itself bogged down in a morass of imprecision: ‘a mist of words’, theory-dependent observation, indefinite objects of study, and the uncertainty of entirely new chemically-based instrumentation, to name just a few of the metrological problems faced by Airy and his assistants. Ironically, during the build up to 1874, the transit of Venus method was often described as especially appealing because of the simplicity of the method of measurement; it was triangulation, like any other survey, and would rely on the kind of ‘direct’ astronomical measurement that had been refined for hundreds of years. Unlike, for example, laboratory-based experiments designed to measure the speed of light, the transit method was of exactly the same class of observation that astronomy’s traditionally privileged status rested upon. The only difference was in the subject of observation: not a transit of a star crossing a wire, but the silhouette of a planet crossing the surface of the sun. As it turned out, that difference was critical. The limits of the Greenwich mastery of the instrumental, human, theoretical and analytic system of precision measurement were exposed. By the late 1870s the worldwide transit enterprise had emerged as an outstanding – yet little-noticed and quickly forgotten – counterpoint to the many success stories of nineteenth-century metrology. Measurement is a circular, iterative process of approximation. Engineers, philosophers and sociologists have all scrutinized the process of measurement, asking how and whether it provides knowledge of the physical world. Both realists and antirealists find ammunition in the complexities of measurement. Some philosophers have argued that scientific progress is best evaluated in terms of the accumulation of observational data. In contrast, sociological studies of the ‘social construction of measurement’ have described how measurement is a ‘contingent, local achievement’, how universality is achieved through ‘a circulation of particulars’.3 Similar studies have argued that measurement is ‘both deeply social and deeply linked to the material world’.4 Historians are also paying increasing attention to measurement. Hasok Chang has charted the process of ‘epistemic iteration’ involved in the history of establishing physical measurements.5 Graeme

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Gooday has recently explored the difficulties in establishing the reliability and trustworthiness of new measuring instruments.6 T. S. Kuhn has argued that scientists today look no further than the textbook presentation of measurement as an unproblematic bedrock of theory.7 For the late nineteenth century, perhaps, the same cannot be said. The transit of Venus enterprise provides an excellent vantage point from which to appreciate Victorian scientists’ intimate familiarity with the complexities of measurement. At the height of the age of precision mechanical instrumentation, before the advent of electronic instrumentation, scientists were especially aware of the ‘uncrossable divide’, as Pierre Duhem put it, between measurer and measurand.8 Consider the remarkable practice of increasing precision by ‘ageing’ chronometers before use. Consider the comprehensive system of auxiliary measurements for systematic error – including human error – that supported every single stellar transit measure. Or consider the ingenious but flawed attempts to precipitate a concrete uniformity from the private, fleeting perceptual judgements that were at the heart of the transit of Venus method. During the preparations for 1882, that deep uncertainty in the observational data became the subject of angst-ridden debate. Even after witnessing the transit of 1874, the correct interpretation of observational data was still essentially inaccessible, even to the observer himself. The debate reveals the dizzying degree to which knowledge could be undermined in the process of analysis. Here is David Gill discussing the problem with Airy in 1880: Take the case of one of the most careful and conscientious observers we have, Captain Tupman, what can be more unsatisfactory than that he actually was afterwards induced to believe that others could more correctly understand and interpret the language in which he recorded and published the results of his own observations than he himself could do.9

As they planned for a much smaller programme in 1882, the very same problems resurfaced, and, surprisingly, the planners found very little use for the personal reports and recollections of the observers in 1874. The situation illustrates how problematic individual knowledge – here tied directly to the process of measurement – could become in scientific practice. From the perspective of this grand unsuccessful measure, the common Victorian rhetoric of measurement takes on a different tone. From this perspective Kelvin’s famous dictum – ‘… when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever that may be’10 – has the sound of a lesson learned from experience. Failure and frustration of the kind explored here has played an important role in motivating that rhetoric of measurement

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as the foundation of scientific knowledge. In the case of the transit of Venus, appreciating the power of measurement went hand in hand with understanding its practical limits.

National Science, Growth and Progress One of the most fundamental historical connections between science and the state lies in the fact that states rely on measurements for governance and control. It should come as no surprise that in Victorian Britain, during a century of massive state expansion, the ‘bigger science’ of the time was largely found in geographical or physical surveys of current or future imperial lands. That kind of science is a hallmark of Victorian Britain, but it is one that is often overlooked – in the shadow perhaps of the monumental developments within the history of ideas of Victorians such as Darwin, Faraday, Kelvin and Maxwell. As important as the intellectual changes were within the culture of Victorian science, the domain of Victorian big science lay with the more stolid, expansionist and patriotic pursuits of the military. A typical picture of the relationship between science and the state portrays the dynamic in terms of science meeting the needs of the state. Sometimes the story also includes powerful interests close to the government that manipulate funding to serve their purposes. On some occasions, however, as this history highlights, there are surprisingly sentimental motivations behind state-funded science. Although perhaps uncommon, it does happen, and sometimes it happens on a sweeping international scale. Such a dynamic was traced by Woolf in the transits of Venus in the eighteenth century, it was traced by Cawood in the Magnetic Crusades, and it has been amply documented here in the enterprise of 1874. The rhetoric of national science carried implications for the internal workings of the transit enterprise. Proctor’s rhetoric of the ‘scientific honour of our country’ was not just floating somewhere on the public surface of this enterprise. Through and through, political ideologies played a causal role in the way the programme unfolded: from MPs’ interest in the enterprise, to Airy’s concern to publish, to his reliance on local advice and talent, to the lack of real international cooperation. The political culture in which the enterprise was embedded touched just about every aspect of the programme, including of course its very existence. The transit enterprise owed its ‘big science’ stature to the existence of nationalistic competitiveness over national scientific reputations. Factors such as these are often underestimated when it comes to understanding the directional growth of science. Whatever the specific local circumstances of their various expressions, such ideologies, naturally bound up as they are with state-funded science, have a

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track record of spurring the ‘big science’ of the nineteenth century as well as that of the twentieth century. It happened with the transit of Venus, it happened with the Magnetic Crusades, it happened with the space race of the 1960s and 70s, and it is almost certainly going to happen again. The case of the transit enterprise also illustrates that growth and progress do not necessarily go together in science. Of course in some sense one goal of science is to expand scientific activity, and in that sense growth can also mean progress. This view is appealing to scholars of science and technology studies because it is a way of describing scientific progress while remaining agnostic about the truth of scientific knowledge. But the consequence of such a view is that very picture of scientific progress, the ‘onward march of science’ quoted from the Sydney Morning Herald in the Introduction, that is so difficult to square with the socially contingent nature of scientific practice. In other words, if growth and progress are decoupled, then a huge amount of the enigmatically unique scientific progress can be understood as part and parcel of the recent explosive growth of civilization and governments in general – part of the growth of state power. If we conflate growth with progress, it makes a progressive or cumulative picture of the history of science inevitable. If we keep them separate, there is much more room for more interesting and more accurate dynamics in our representations of the history of science.

EPILOGUE: THE TRANSIT OF 1882

The discussion which took place, and the innumerable articles which appeared in every journal, (the Echo included), at the time of the 1874 transit must have familiarised the nation at large with the fact that these transits of Venus are regarded by astronomers as affording an excellent, if not the best, method of determining what is technically known as solar parallax. The Echo, 1 March 1881 I do not think a method which allows an observer only one observation as the result of a costly expedition can be a good method … But the Transit of Venus carries an undue traditional importance, even amongst some astronomers, as a parallax-determining method; and we must try to observe it as well as we can. David Gill to George Airy, 18801 Whatever we may consider as concluded from the observations of the transit of Venus, 1874, I think we may well believe that the scientific world will not be satisfied unless we take the opportunity of securing all that can be obtained from the Transit of 1882: such an opportunity as will recur only after the extinction of three generations of mankind. George Airy, May 18802

Back in 1857, when Airy first described plans to observe the transits of Venus, he had proposed to devote most attention to the transit of 1882. The circumstances of the 1882 transit were more favourable for a few reasons: the transit duration was longer and thus its measure should have a smaller degree of error, and the entire transit would be visible from existing observatories throughout North America. The transit of 1882 should have brought an even larger effort by the astronomical community. An article in the New York Times put a cynical and wildly inaccurate spin on the ‘great popular transit’, making the claim that astronomers in 1874 had purposely hidden the fact that there was to be a transit of Venus in 1882 (and that they also hid the fact that a ‘transit [sic – confused with Mars in ascension] of Mars’, which allegedly could just as well be used to measure the parallax, had been due in 1877). The article cast astronomers as a frivolous, leisurely class that leeched on public money and jealously guarded scientific knowledge. It mocked the motives of expedition astronomers: ‘It has finally become evident to all – 153 –

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thinking people that so long as astronomers can induce Governments to send them to China and Peru the necessity of observing transits of Venus will never come to an end, and the distance of the sun from the earth will never be definitely settled’. And it was only because the American astronomers were afraid to ask the government for money that they were observing it from their home country, side by side with the ‘unlearned common people’ who ‘for the first time in the memory of man’ had also been ‘permitted’ to view it.3 In reality, the American astronomers did ask for money from their government and had received a grant of $83,000 to send stations to the southern hemisphere. These observations would be compared to those being made at dozens of observatories throughout the United States. However, as in Britain, and despite the fact that the transit was visible throughout the country, there was much less enthusiasm and government support for the 1882 expeditions. It is not surprising that, after the experience of 1874, this should be the case. Not only had the utility of the transit of Venus method been called into question, but also, in Britain at least, the transit of 1874 had consumed even more money than the projected cost for the combined efforts of 1874 and 1882. On top of that, other methods of measuring the sun’s distance were now showing clear signs of success. Although the newspapers still often described the method as a favourite among astronomers, ‘if not the best’, the truth, as the second and third epigraphs to this chapter suggest, was that the reasons driving the second attempt (such as the transit’s ‘traditional importance’, and a concern about ‘satisfying’ the ‘scientific world’) were much less solid or even rational. Although most astronomers, like Stone and even Airy, expressed scepticism about the transit method, there was still the attitude that, as Airy told the Chief Hydrographer in March 1880, ‘We must observe it’.4 Just what prompted such devotion is one of the more interesting questions to ask about the 1882 effort. Only the astronomers of Pulkovo stated the failure of the transit method plainly, letting the 1882 transit pass without making an effort to observe it.5 That effort was made with less energy, resource and ambition. The preparations would only begin in late 1880, there would be fewer expeditions, and the results would be churned out within a relatively short period. But it was not just a shrunken version of the 1874 enterprise. Different people and institutions were involved, and they employed new modes of management and a revised approach to the challenge of measuring contacts. Some of those changes – especially the more concerted effort at international organization – are evidence of larger, more sustained developments in late nineteenth-century astronomy. Others, like the rejection of photography in 1882, run contrary to the general historical trends of the period. In all, the very different nature of the transit programme for 1882 adds to our understanding of both the failures and successes of the 1874 effort,

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and, more generally, subsequent developments at Greenwich and in astronomical photography and international scientific cooperation. A brief note about the difference in source material for the two transits should be made. In general, there is much less of an archival record of the 1882 programme. This is true for the operation of the management as well as for the expeditions. For example, while letters and diaries (some of them very detailed) exist for at least five observers of the 1874 transit, none is known to exist from 1882. In the archives of the Royal Observatory, sixteen boxes, each containing hundreds of papers, record the growth and decline of the 1874 enterprise in detail. There is only one box for the papers of 1882.

Change of Leadership and Loss of Resources Airy, who was still Astronomer Royal when plans for the 1882 transit began to materialize, had from the start made it clear that he was not going to superintend the transit of 1882. Early on, he took steps towards transferring that responsibility onto other shoulders. In September 1880, he submitted to the Admiralty a plan, which included a list of favourable stations, a description of methods to be used, and the suggestion that Edward Stone, now the Radcliffe Observer in Oxford, ‘upon whose time the government (I believe) has some claim’, should take on the role of superintendent.6 Airy made little effort to justify repeating the effort to measure parallax from the transits of Venus, stating only that it was of ‘superior importance’ (conditions-wise) and that ‘probably the observations can be completed at a very small expense’. An 1882 programme seems to have been, regardless of the results from 1874, simply expected.7 With Airy having stepped back from the issue, the Admiralty placed it on the plate of the Royal Society, requesting that a committee be formed to advise the government on how to proceed. This committee consisted of William Spottiswoode, the current President of the Royal Society, J. R Hind, the current President of the Royal Astronomical Society, and T. H. Huxley, a high-profile figure among scientists and the public alike. In mid-December, the committee submitted its report, providing outlines for the station distribution (building on Airy’s recommendations), longitude methods, and the personnel and instruments required. The budget, much more complete than any budgets for 1874 had been, was set at £15,450.8 As for management of the programme, the committee suggested forming a larger and more permanent transit of Venus committee: In preference to placing the proposed Observations of the Transit of Venus in 1882 under the direction of a single individual however eminent, the committee would advise the appointment of a special committee to decide upon the observations which are essential and to advise the government the best method of carrying them out.9

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Airy was characteristically sceptical of the committee model of management. It seemed to him, as he told the Admiralty after they asked for his opinion, impossible to manage effectively except ‘by the agency of one superintendent … a person acquainted with the whole train of the work’.10 But Airy’s opinion was now much less influential, and a second transit of Venus managing committee was approved. Although the Admiralty made no complaints about the proposal, it informed the Treasury in early January 1881 that, ‘while a Transit of Venus expedition in 1882 is considered desirable, my Lords are unwilling to undertake the expense’.11 This could have been the end of the 1882 effort, but instead the Treasury decided to run the programme as a Royal commission. This meant that the transit of Venus committee would communicate directly with the Treasury, which would maintain control over all expenditures. The committee chair was responsible for the overall budget, and each station would have a ‘sub-accountant’, who was instructed to incur only ‘absolutely necessary’ expenses.12 As we will see, it was not unusual for the committee’s funding requests to be rejected by the Treasury.13 The financial situation was tight, and, to make things worse, many of the benefits associated with being an Admiralty project – apparently ‘free’ transport, labour and even supplies – were simply not available to the 1882 organizers. The same was true with regard to astronomical instruments; now that the programme was no longer aligned with Greenwich, the committee had to fight for access to government-owned instruments. Many of the instruments built for 1874 had been dispersed either to the College of Royal Engineers, the Special Loan Collection of the Science and Art Department, or to the colonial office. The committee could apply to the Science and Art Department for loan of the instruments that had been deposited there, but in all, three new equatorials (by Cooke and Grubb) and three new telescopes (by Grubb and Simms) were purchased at a total cost of £980.14 Instruments were also borrowed from Lindsay, and an advertisement was placed in The Times asking about any astronomers who ‘have at their disposal and are willing to lend’ instruments such as 4-inch, 5-inch and 6-inch refractors, 10-inch and 12-inch reflectors on equatorial mountings, and altazimuths.15 The transit committee held its first meeting on 24 January 1881. Somewhat surprisingly, Warren De La Rue was among the members; this may be taken as a sign of both his high standing in the Royal Society and of the fact that he was not directly implicated in the failure of the photographic plan of 1874. The other seats were held by John Couch Adams, Airy (who was only ever present via correspondence), Lord Lindsay, J. R. Hind, William Huggins, George Richards, W. H. Smith, George Stokes and Edward Stone. The membership made up an even balance of private astronomers (Lindsay, De La Rue and Huggins), professional astronomers (Adams and Stokes from Cambridge, Airy, and Stone from

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Oxford) and naval administrators (Hind from the Nautical Almanac, Richards, the Chief Hydrographer, and Smith, formerly First Lord of the Admiralty). A few weeks after the first meeting, an editorial in the London Echo reiterated Airy’s feeling that the committee model of management was a weak one. The ‘hardly earned money of the British taxpayer’ was thus in danger of being squandered: Common sense would dictate that in the case of such an expedition, one paramount and responsible Chief could alone be depended upon to organize and direct it … but no! … A committee appointed by the Royal Society at the request of the Government (!) … the idea of a Committee directing such an expedition at all is supremely ridiculous. Many a bad army has prospered under a bad commander; but no army has ever prospered under a debating society.16

The editorial further argued that the government should have chosen the Royal Astronomical Society rather than the Royal Society to manage the programme, partly because of the recent alleged failures of other taxpayer-funded Royal Society projects, from the Society’s 1875 eclipse expedition (a ‘miserable abortion’) to the Special Loan Collection (a ‘shameful waste of public money’). The fact that the Royal Society was allotted the transit of Venus commission only proved, according to the author, that it was dependent upon on ‘jobbing’ and ‘wirepulling’, rather than real utility or effectiveness, for its survival. In obvious ways, the Royal Astronomical Society would have been a more natural choice. But the Royal Society did have a much closer connection to the government and its funds than did the Royal Astronomical Society. At the time, it was the only body to administer governmental grants for scientific research. Moreover, in practice, the two societies had such an overlap in membership that the Royal Astronomical Society was well represented on the transit committee; in fact, all but Smith were members of the Royal Astronomical Society. In the summer of 1881, Stone was elected Directing Astronomer for the committee. The majority of the work involved in training the observers, organizing the expeditions and reducing the results would now be relocated to the Radcliffe Observatory, which itself was a struggling institution. Airy had written it off as ‘of no use to the world’ in 1872,17 and its reputation and financial situation had not improved by the time Stone took over in 1878. Roger Hutchins has described Stone’s directorship as a management of over twenty years of obsolescence. According to Hutchins, university observatories in general had a very low profile during the 1870s, squeezed between Greenwich and the grand amateurs, and of those university observatories, the Radcliffe was among the most poorly equipped.18 The management of the transit programme was thus transferred from the most prestigious scientific institution in Britain to one of the least significant ones.

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The Question of International Cooperation First on the committee agenda was the issue of international cooperation: what were other countries doing, and to what extent should collaboration be pursued? Through the Foreign Office (rather than, as happened in 1874, through Airy’s personal communications), queries were sent to France, Germany, Italy, Russia and the major colonies. It was suggested that a collaborative effort with the United States – where the entire transit would be visible – might be proposed, and the committee put the following question to Airy: Are we (the English nation) to undertake a series of observations which are complete in themselves, or are we to cooperate with other nations in such a manner that the series of observations undertaken shall be complete as a whole … so as to avoid the labour and expense of duplicate observations.19

Given the need for efficiency and the reduced expectations for precision in the results, a truly collaborative international effort – e.g., each country observing the transit in its territory, and the results being combined – may have seemed more appropriate for 1882. Airy, however, was resolutely against any international collaboration. He believed each country must produce a complete set of observations, and that transnational mixing of observations would not produce a trustworthy result: I do not mean that the general plan of one nation should in any degree be concealed from another nation or should be unaffected by the understood plans of another nation … but there would infallibly be distrust in the combination of results of France ingress accelerated with England ingress retarded.20

In a later letter he added: I might have mentioned that in Royal Sound of Kerguelen’s Land three stations met (German, American, English) and at Thebes two (German, English) in friendly communication with comparison of chronometers etc., but no one thought of mingling the results.21

In Airy’s mind, the nature of the transit of Venus enterprise was entirely unsuitable to collaboration, regardless of how much strategic sense it might have made.22 Airy claimed that Admiral Mouchez, director of the Paris Observatory, felt the same, and a letter from Mouchez confirmed it, yet a letter to Spottiswoode from Cornu, a member of the French commission for 1882, seems to suggest the opposite.23 In the end, there would be much more organization on the international level than in the transit of 1874, and it was France that pushed the way forward. An international commission on the 1882 transit was held in Paris on 17 October 1881, coinciding with L’Exposition Internationale de l’Electricité. In

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many ways, the commission was a success and there was a remarkably international constituency, including participants from the Argentine Republic, Brazil, Chile, Denmark, France, Germany, Holland, Mexico, Portugal and Spain.24 Surprisingly, the United States did not attend. Britain could only send a few representatives, and these had to pay their own way. The British commission had applied to the Treasury for funds to send a proper delegation, but the application was rejected. A letter between the Foreign Office and the French ambassador reveals that the Treasury saw ‘no justification’ for sending delegates to the commission and was of the opinion that the commission ‘may or may not include the best astronomical representatives of the countries sending out observers’. The Treasury therefore suggested the official invitation reply should be to the effect that: The arrangements for the British observing parties and for the expense to be incurred have reached a stage which does not admit of sending delegates to the proposed commission and that her majesty’s government can only express their regret, therefore at being unable to co-operate in it.25

Without the presence of representatives from the United States, and with only slight support from Britain, the international commission at Paris lost a significant amount of its influence. Nevertheless, its level of organization was substantial and a number of points were agreed upon among the participants. There was, for example, the near-universal rejection of photography as an instrument for observing the transit; aside from America, only France would use photographs at two stations. In addition, a second conference was to be held in 1883 in order to form agreement on how to proceed with the data.26 The most important result of the commission was the adoption of a standard set of instructions for observers, which all countries except Britain and America would adopt. For a number of reasons to be addressed below, these instructions, and those of Britain and America, would be of central importance to the 1882 programme.

The New Instructions to Observers In 1874, the British plan had been to train the observers on the model so that they would all recognize the same phenomenon, or phase of ingress or egress, as ‘contact’. In 1882, a different approach was taken: reduce the error by increasing the number of observers. The larger the data set, the better the chance that an average of the times chosen as ‘contact’ would cancel out any random errors in observer judgement or perception. So, whereas in 1874 the set of observers was strictly intended to include only those who had received the proper training (although in the end data from a number of untrained observers, e.g. Emily Newton, were included in the final reports), in 1882 there was an open call for

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astronomers everywhere to participate. The idea was that ‘by securing, if possible, a considerable number of observations, the mean phases observed for “transit accelerated” would be sensibly the same as that for “transit retarded” which is all that is required for the determination of an exact value of the Sun’s distance from a discussion of such contact observations’.27 Thus, a detailed set of instructions would be printed and widely distributed throughout North America, Australasia and other populated areas where the transit would be visible. There was also a core of hired observers. With the selection of these observers, many of whom had participated in 1874, the committee was somewhat discriminating. Airy had given his opinion of the candidates for observers whom he knew and his views were followed. George Forbes, for example, was described as ‘a clever man, but more inclined to speculate on something new than to rely on anything old. Fancy may outweigh judgment.’28 He was not offered a post. In the end, nine of the sixteen hired observers were pulled from those who had participated in the transit of 1874. All of them underwent model training at the Radcliffe Observatory. This time, there was not the same focus on learning to distinguish the phases of the model black drop. Rather, as Airy had repeatedly stressed, the model was to be used to provide a general sense of what the transit would be like. Without some model training, ‘nobody can conceive of the punishing slowness of the planet’s relative motion’.29 As for the instructions, the committee took great care in formulating them. The first draft had been started by Airy in October 1880 and was later passed on to the committee. Largely, this was a straightforward adaptation of the 1874 instructions. The recommended instruments, for example, were the same. One new addition, made at Airy’s insistence, was a compendium of the observations in the previous transits of 1761, 1769 and 1874. This was Airy’s solution to the problem that model training would not be available to all observers; it was a surrogate for the model, a way to provide observers with a sense of what to expect. One of the most debated points concerned how to instruct observers to record contact. According to one view, the best chance of success lay in directing observers to record everything they saw, thus indicating a number of times along with descriptions of the phenomena at those times, and to be descriptive, supplementing the reports with drawings where possible. Times then could later be selected, as Tupman had done with the 1874 data, across different reports that seemed to describe similar phases of contact. A different approach advocated that each observer should only record a single time for contact. This view was strongly promoted by David Gill, who was now Astronomer Royal at the Cape of Good Hope. As one of the astronomers who had been chosen to give a second analysis of the 1874 data, Gill could speak from experience about the disadvantages of Tupman’s phases method. Gill argued that a system that left open the possibility of multiple interpretations

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was just as bad, perhaps worse, than a system that might produce less data and less accurate figures but which was not open to the problems of interpretation. He suggested that observers should be instructed to seek the appearance of the ‘brown tinge’ (‘viz. for internal contacts at egress when the black between the limbs of Venus and the sun begins to change from black to brown’) at contact, and to record this phase or none at all. It is to avail the utterly unsatisfactory state of the things which resulted from the last transit that I would urge this. It is much better that an observation should be lost than that an observation should be employed about which there can be two opinions. Take the case of one of the most careful and conscientious observers we have, Captain Tupman, what can be more unsatisfactory than that he actually was afterwards induced to believe that others could more correctly understand and interpret the language in which he recorded and published the results of his own observations than he himself could do. Unless one phase is selected we shall have the same thing again.30

The committee had interviewed some of the 1874 observers about their reports of contact, and Tupman’s apparent confusion over the meaning of his own words may have come out during his interview.31 In general, not just in Tupman’s case, the memory and recollections of observers could not easily be put to concrete use by the committee, and the nature of contact remained as frustratingly inaccessible as before the transit of 1874. This pointed at a fundamental problem with the transit of Venus method. Gill was challenging the committee to face up to just how problematic the observer descriptions of contact were as evidence or data for precision measurement. Even those who had once observed contact were now unable to hold together the evidence of their own senses and the language they used to present that evidence. And if the authority of the observer himself is undermined, this leaves the data open to multiple interpretations. There were, however, obvious risks to taking such a severe approach. Airy was certain it would ‘ruin’ the observations, and the commission generally agreed with him.32 So, in the final form of the instructions, a sort of compromise between Gill’s and the more relaxed approach was adopted. The observers were instructed to give the time of contact as exactly as possible, but not to be discouraged by an uncertainty of a few seconds; to give drawings and clear descriptions illustrative of the phases observed; not to multiply time records unnecessarily; and, finally, to give as accurately as possible the time when the limbs of Venus and of the Sun, mentally completed, would appear to touch.33

Here, too, is the final form in which the phenomenon of contact was described for the 1882 observers. They were to seek ‘the time when the limbs of Venus and the Sun, mentally completed, would appear to touch’. The bizarreness of such an instruction – and a return to psychological judgement – indicates what a strug-

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gle it had been for the committee, and indeed for Airy and Tupman before that, to pin down clearly in words just what contact was. Not surprisingly, this is also the point at which were some disparities between the American, the British and the international instructions.34 In general, the instructions were similar and, as Spottiswoode explained in an address to the Royal Society, ‘it is hoped, from the close agreement between the instructions issued to the different observers, that the whole may ultimately be available for combination in to one general discussion’.35 But the sections that described what the observer should look for to call ‘contact’ were different in subtle but apparently critical ways. For example, for ingress, the Americans directed observers to the closing of the bright cusps, while the British directed attention to the disappearance of the dark break in the sun’s limb. Newcomb had expressed serious concern over the form in which the appearances at contact were described in the international instructions. Here, observers were instructed, in a way similar to the British instructions, to seek contact at ingress in the form of a ‘discontinuity in the illumination of the apparent limb of the sun’.36 To Newcomb, this sounded the same as seeking the formation or the break of the black drop. He was adamant that the attention of the observers should be directed at the cusps either coming together or separating. He argued on the one hand that it was simply more difficult to clearly explain what observers should look for in a formation or breaking of light, or ‘shadow on the light’ as it was once described. And he argued on the other hand that the experience with the American artificial transit of Venus (which, as was described in Chapter 1, was viewed from over a mile away to allow for the effects of atmosphere) demonstrated that, while the shadows and ligaments change drastically due to atmospheric conditions, what remained constant was the rate of the cusps separating or joining. But Newcomb’s complaint did not alter the British or the international instructions. In the end, it is difficult to say whether the differences mattered. From the outside, all of the descriptions of contact can appear equally vague, and the supposed distinctions between them can be dizzying. What the debate does convey, however, is how, even after the passage of 1874, the phenomenon at the very heart of the transit method resisted all attempts at quantification, clarification or even an unambiguous description.

The Longitude Work and the Loss of Admiralty Patronage In the transit of 1874, Airy had been sceptical of both chronometric and telegraphic methods of longitude, and had planned to employ the lunar distance method at all stations. By 1880, however, any doubts about these new methods had been resolved and the transit committee (Airy included), hoped to rely upon them entirely. Telegraphy, including submarine telegraphy, was now

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trusted, cheap and relatively quick. Transit observation stations were thus often selected based on their proximity to telegraph lines, and only two of the selected stations, in Bermuda and Madagascar, did not have connections. In those cases, chronometer runs connected them to the nearest point of communication. Throughout the 1870s, Britain’s communications empire had expanded at a rapid pace. Cables had been laid to Australia, New Zealand and the Cape of Good Hope. Telegraphically determined longitudes were following close behind, building outwards in a chain from Greenwich into the colonial territories. The 1882 transit gave Greenwich a reason to push for extending the chain all the way to Sydney. Airy strongly promoted determining the longitude of Sydney (and thus all other observatories in Australia and New Zealand) as part of the 1882 transit.37 Prominent thanks are given in the 1882 report to the directors, station managers and line operators of the Eastern Extension Australasia and China Telegraph Company, attesting to the central role played by the communications industry in the longitude work of 1882. The same could not be said of the Admiralty, which refused to transport personnel and instruments to Singapore, where the final link of the SydneyGreenwich chain was to be closed. Upon being approached for assistance, the Admiralty and the Board of Trade jointly replied that ‘neither in the interests of Her Majesty’s ships nor of the mercantile marine were such signals required of as far as the navy is concerned’.38 The Admiralty’s refusal to transport one man and a box of instruments is a clear sign of the growing distance between astronomy and navigation. Airy had fought against such change. During his last report to the Board of Visitors before he retired, Airy noted ‘with grief ’ how the Admiralty had ‘entirely abandoned the longitudes of the Atlantic which have been cleared away before our eyes by the scientific enterprise of another nation [the United States coastal survey]’. And the situation was equally poor for British territories: ‘The Pacific, bearing those vast and important colonies, almost entirely British, is equally neglected, though so much is ready that the mission of a single officer would quickly establish all’.39 If this was meant to be a challenge to the Admiralty to defend their scientific achievements, it did not succeed in rousing any such response. On the contrary, the reply was devastatingly utilitarian: ‘My lords fail to perceive that England here has been guilty of neglect’, wrote the Secretary of the Board of the Admiralty to the Secretary of the Board of Visitors at Greenwich. It simply would have been ‘ungracious’ to repeat the same work that the Americans had just completed. In fact, the Admiralty welcomed this ‘rivalry, if such it may be termed’, for it would ‘add to the common stock of accurate science’.40 Clearly, the Admiralty was no longer concerned about competing in any sense over longitude work – there were now other arenas, especially Arctic and

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Antarctic exploration, that offered more important symbols of scientific enterprise. As the rest of the Admiralty’s reply made clear, this new situation was a real threat to Greenwich astronomy. A line between the ‘accurate knowledge’ of longitudes required to meet the ‘general interests of navigation’ and the ‘scientific accuracy’ pursued by astronomers for their own purposes was being drawn.41 The Admiralty was increasingly reluctant to support the latter. In the end, the committee found another way to transport an observer (Leonard Darwin, son of Charles Darwin, who also observed in 1874) to Singapore. According to the final report on the 1882 transit, the completion of this telegraphic longitude network was one of the most important auxiliary benefits of the transit programme.

The Expeditions To-day will hear the tinkling chime Of many a ringing silver dime, For him whose optic glass supplies The crowd with astronomic eyes, – The Galileo of the Mall. Oliver Wendell Holmes, ‘The Flâneur: Boston Common, December 6, 1882, During the Transit of Venus’42

The seven official observation stations sent out by the Royal Society committee were distributed at Jamaica, Bermuda, Barbados, Cape Colony, Madagascar, New Zealand and Brisbane. At all stations except the one in Brisbane, the weather was clear. Observations from volunteers were also gathered from the Cape of Good Hope, Natal, Mauritius, Australia, New Zealand and Canada. More often than in the previous transit, the stations were placed in colonial territories, presumably another way of keeping the costs down. The committee gave thanks to the colonial governments of Canada, Victoria, New South Wales, South Australia, Queensland, New Zealand, Mauritius, Natal and the Cape of Good Hope for their material support and for ‘the equipment of Colonial observers who have taken an important part in the observations’.43 In all, thirty-six observers would be volunteers from the colonies, compared to the sixteen observers hired by the committee. George Tupman, now a colonel, was chief of the New Zealand station. The Jesuits Perry and Sidegreaves were at Madagascar.44 Though the Admiralty was no longer in charge of the expeditions, military personnel still formed the majority of observers. Ten of the observers were associated with the military or civil service; the Royal Artillery, Royal Marine Artillery, Marine Artillery, Royal Navy or the Royal Engineers. Each station also had one assistant from the Royal Marine Artillery.

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As stated earlier, very little archival material survives from the expeditions of 1882. Unlike the expeditions of 1874, no personal accounts, letters between observers or other records of the expeditions have been found. That is the result both of Airy’s absence (he was a notoriously thorough archivist) and the smaller duration and scale of the 1882 expeditions. What do survive are many more accounts of the public experience of the transit, a reflection of the much larger English-speaking public that viewed it. In the British public eye, the 1882 transit was much less visible than the 1874 transit had been. In The Times, for example, the transit of Venus appeared seventy-six times in the years 1873–5, while it only appeared twenty-one times during 1881–3. Nevertheless, as part of the transit would be visible in Britain, it was still presented to the public, though this time under a much less patriotic or serious light. One example of the popularization of the transit comes from Thomas Hardy’s Two on a Tower (1882), which was first serialized in the Atlantic Monthly during the eight months leading up to the transit of 1882. The book tells the story of Swithin St Cleeve, an amateur astronomer, who forsakes his (older, married and pregnant) lover to embark on a worldwide adventure culminating in an observation of the transit of Venus. While his lover resigns herself to fate (‘This would be on the eve of the Transit, and what liklihood was there that a young man, full of ardour for that spectacle, would forego it at the last minute to return to a humdrum domesticity with a woman who was no longer a novelty?’), St Cleeve’s astronomical ‘pilgrimage’ takes him around the globe not only to observe the transit but also to look through the famous telescopes of the world (in Vienna, Pulkovo, Harvard and Chicago).45 Like the astronomers, the press was drawn to the transit’s rarity; it was now ‘the last transit for 122 years’, where as in 1874 it had been ‘the first transit in 125 years’. On the day of the transit, The Times published an upbeat article by Christie, in which he confidently expressed the hope of success, describing the transit as ‘affording one of the best means of determining the distance to the sun’. He even praised transit photography, noting that ‘there is sufficient encouragement to try it again’.46 As for seeing the transit in England, astronomers and the public were both disappointed; clouds and snow obscured all views of the event. An article the next day was devoted to the history of transits of Venus, especially the ‘prominent part’ played by Englishmen in that history, starting of course with Jeremiah Horrox in the seventeenth century.47 In the following days, Stone relayed telegrams from stations regarding weather and general success or failure.48 As it had been for Asia in 1874, the transit of 1882 was a public spectacle throughout North America. It was heralded by the New York Times as ‘a great popular transit’ and a ‘popular exhibition’. In New York City:

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The Transit of Venus A very satisfactory view was obtained through smoked glasses, but the speck which was made on the disk of the sun by the planet was so small that it required some time of close application to the glass before it was recognizable. Enterprising proprietors of telescopes of all sizes and powers stationed themselves in favorable places all over the City, and reaped a large harvest by exhibiting the planet on its journey across the sun at the rate of 10 cents a sight. In the City Hall Park a telescope was erected and so great was the rush of people to take a look through it that the services of a Park policeman were required to keep them in line awaiting their turn … A telescope was mounted on Broad-street, near the Stock Exchange, and the owner of this, too, had all the business he could attend to … Broad and Wall streets were filled with bulls and bears, each with a piece of smoked glass in his hand, and when not engaged in scientifically examining the transit, they amused themselves by blacking each other’s noses and faces … The 120 boys of the Berkeley School … and over 2,000 other people viewed the transit through a new telescope with a 4-inch glass … Scores of Columbia College students wearing mortar board caps climbed to the top of the new law school building of the college yesterday to catch a glimpse of the transit.49

The Outcome On the issue where it would seem most valuable (and crucial) to have had the experience of 1874 to draw upon – dealing with the phenomena of contact – those private experiences of the observers were, in the end, as Tupman’s inability to interpret his own report showed, almost useless. In 1882, contact remained as mysterious and inaccessible as it had been before 1874, when no one alive had witnessed it. Although Gill advocated taking the bold approach of removing descriptive language from the reports entirely, the committee would not take such a radical step. Stone, in his analysis of the observer reports, would face the same ‘mist of words’ that had confounded the analysis of the transit data from 1874. Over the next decade, without much fanfare, Britain, Germany, America, France and Russia produced their results. Stone was in charge of producing the British report, which was published in 1889. H. J. Carpenter, formerly a computer at Greenwich, was responsible for most of the arithmetical work. Stone’s preface acknowledged the central difficulty of the transit contact method (‘… the possibility that the recorded times for internal contact might refer to phases which take place with different angles of separation of the limbs’), the solution attempted (‘… by securing a considerable number of observations, the mean phase observed for “transit accelerated” would be sensibly the same as that for “transit retarded”, which is all that is required …’), and the subdued expectations about the result (‘… these requirements have largely been met’).50 The longitude calculations and reductions, such a substantial part of the 1874 publication, were not included in the 1882 report, making for a much more compact volume. For

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the most part, it is devoted to the fifty-four transcripts of observer reports that would form the basis of the calculations. Stone’s method of analysing the contact data was a slimmed-down version of Tupman’s approach to the 1874 data: phases of the contacts were defined and observations were sorted accordingly.51 The observations were combined in different ways – either sorted according to different phases, or rejected according to certain criteria – to produce eight possible results for the solar parallax as derived from comparisons of internal contact observations at accelerated and retarded ingress. The final value, 8˝.823 ± 0.034 (149.1m km / 92.6m mi ± 1.2m km / 755,000 mi), was settled on as ‘the best result which the observations here discussed afford’, and for the most part it disregards the earlier separation of observations according to phases; the Cape observations and those of Talmage and Stevens were all included.52 The driving factor seems to have been to retain as many observations as possible, or at least, not to reject the Cape observations. One of the observer’s times, that of Hall at the ingress-retarded station of Jamaica, was modified to be earlier by some seconds, possibly in order to help balance the apparently early times of the (ingress-accelerated) Cape observations. The observations of contact at egress proved more difficult and did not conform as well to the phases of contact that Stone had defined for ingress. In general, observers gave more observations over a longer period, making room for an even greater range of possible results. In this case, Stone chose not to use phases but to take the first times, last times, and mean times of each observer. The official result, where the mean of the results from contacts at ingress and egress are combined, is reported as 8˝.832 ± 0˝.024 or 92,560,000 ± 250,000 miles. It should be noted that the margin of error is much smaller than in either Stone or Tupman’s analysis of the 1874 data (8˝.884 ± 0.123 for Stone and 8˝.760 ± 0.122. for Tupman). In this sense, the results for 1882 did improve upon on the results of 1874. The transit method of finding parallax was finally, after 1882, acknowledged as among the worst of parallax measurement methods. More generally, although the experimental modelling techniques and photographic methods of 1874 were not successful, this did not preclude later development and investment in those very areas. At the same time, it is difficult to find examples of how the experience of the failed transit enterprise was integrated into later research programmes. One area where there was significant development was in the administration of such a large research programme. Proving Airy’s pessimism about the committee model of management unjustified, the transit committee seems to have been successful and efficient in organizing both the preparations for the expeditions and the analysis of results. And, with a more detailed budget and a more substantial structure for financial reporting and accountability, the 1882

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programme was on the road to correcting one major failing of 1874: massive overspending.53 Thus, in terms of programme management at least, the movement of the programme operation from Greenwich, where it was at the centre of British astronomy, to the periphery at the Radcliffe Observatory, Oxford, and from Airy to the Royal Society committee, was a positive one.

The Transit Enterprise, International Cooperation and Precision Astronomical Photography As described in the Conclusion, the failure of the transit enterprise stands out in a period otherwise known for its advances in precision measurement. This section concludes with a description of two further areas in which the British transit enterprise stands against some broader historical trends of the period: the growth of international cooperation and the spread of precision astronomical photography. The Conferénce Internationale des Etoiles Fondamentales was just one of a number of new international efforts in astronomy from around 1880. Perhaps the most significant sign of the new strength of international cooperation in astronomy came at a meeting of the International Geodetic Association in 1884, when twenty-seven countries agreed to adopt the Greenwich meridian as the standard zero of longitude. Three years later, one of the most ambitious cooperative international research programmes, the Carte du Ciel, was begun. These efforts were much more successful in producing agreement, standards, and productive working relationships than the transit enterprise had ever been. The Carte du Ciel was an ambitious attempt to employ photography in cataloguing and mapping the night sky to new levels of detail. According to the Carte du Ciel’s official historian, the programme ‘marked the systematic introduction of photography into astronomy’.54 It may be more correct, however, to say that it marked the successful systematic introduction of photography into astronomy; the scope of the photographic programmes of the 1874 transit of Venus must certainly count as an attempt to introduce photography into astronomy on a wide scale. However, it is true that the Carte du Ciel was part of the ‘watershed of the 1880s’ as historian John Lankford describes it, in which photographic research, aside from its rejection for the 1882 transit of Venus, expanded significantly.55 Part of the new success of photography had to do with developments in photographic technology, including the commercial manufacture of dry-plate gelatine film, which was cheaper, more convenient and more reliable. Photographic telescopes had also been improving. For the specifications of the Carte du Ciel instruments, the short-focus method was chosen over any long-focus instrumentation, but with enlarging lenses that were better corrected for spherical aberration and chromatic distortion. Such standards were enforced by the Comité International Permanent pour l’Exécution Photographique de La Carte du Ciel, perhaps one of the most influ-

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ential international scientific committees of the time. Over the twenty years of its operation (before it was absorbed by the International Astronomical Union), the Permanent Committee became the major forum for discussions of photographic astronomy, and its work was reported and reviewed in all the European and American astronomical journals. According to Lankford, it would be difficult to overestimate the educational functions of the Committee.56 Nevertheless, some of the very same problems that had plagued the transit photography were still being struggled with in the Carte du Ciel – and in astronomical photography generally – at the beginning of the twentieth century. In particular, the challenge of stellar photometry, which required the measurement of the diameter of the ‘disk’ of a star to assign it a magnitude, faced similar setbacks. Problems arose over the establishment of a standard scale by which to compare the sizes of the star disks, and this was compounded by technical difficulties in obtaining uniform measures of the same stars across different plates and at different observatories. Every star in the Carte du Ciel was to be assigned a magnitude, so the disagreements over stellar photometry were of central concern to the Permanent Committee, and yet many of the issues were not resolved until after 1910. As with the diameters of Venus and the sun in transit photography, the sensitivity of the film, local atmospheric conditions, and the optical characteristics of the instruments all affected the photographic size of the stars. Lack of agreement on the physics and chemistry of the photographic process was also problematic; many astronomers continued to assume that the action of light on the photographic plate was independent of its wavelength, though the opposite had been argued by Newcomb as early as 1872. The optics of the photographic enlarger was also crucial but poorly understood. Studies by K. Schwarzschild in Vienna suggested that diffraction significantly affected the size of star images at varying distances from the optical axis, and he argued that the measurement of image diameter could not provide an accurate gauge of magnitude. Measuring the diameter itself was fraught with difficulty, as Abney explained in 1891: ‘anybody who has attempted to measure the disk of a star will know that it is a rather shaky thing to do. It is very difficult to say where the disk extends to and where it does not.’57 Clearly, some of the problems that had led Christie, Tupman and Airy to abandon the transit photography ran deeper and wider than just the transit of Venus programme. The Carte du Ciel also ran into similar financial problems as the transit enterprise had. Its completion took much more time and money than had been expected. Initially expected to take three years, the catalogue was not completed until 1964. The cost of just Oxford’s portion of the map, which was smaller and less complete than those of the larger national observatories, was put at £34,000. Participants in the Carte du Ciel were thus saddled with an unexpectedly heavy burden, and historians disagree whether the project as a whole was a stimulant

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or retardant for the growth of astronomy. Lankford concludes that the faster growth of astrophysics in the United States during the early decades of the twentieth century may be due in part to its non-participation in the Carte du Ciel.58 If the same question were posed about the transit of Venus, it would be difficult to assign either a positive or a negative effect of the enterprise upon astronomy in the participating countries. Greenwich seems not to have been harmed by its preoccupation with the transit of 1874. Under Christie, Greenwich diversified its research interests and slowly expanded. Although the old ties to the Admiralty and government funding through longitude work had been significantly weakened, new ties were being formed. As Christie turned Greenwich successfully towards research in astrophysics, government support for the institution expanded. New positions were added and new instrumentation was introduced to the observatory’s routine. In 1860 the cost of operation at Greenwich had been £4,300 and by 1900 it had risen to £9,000.59 One of the instruments introduced to Greenwich under Christie was a multipurpose modelling device that was used for training and testing for effects of personality in various observations. Greenwich also participated fully in the new efforts in astronomical photography. The daily solar spot measures begun by De La Rue at Kew in 1864 were continued at Greenwich, using one of the transit photoheliographs, from 1873 to 1885. The results, a tabulation of the motions and dilations of the major sunspots, were published in 1907.60 Another of De La Rue’s instruments also continued to be successfully applied to quantitative photography at Oxford University Observatory. In 1886, Charles Pritchard, announcing the successful measurement of stellar parallax using the 13-inch reflector built by De La Rue in the early 1870s, told his board of visitors: The somewhat hazardous enterprise of attempting, for the first time in the history of astronomy, to obtain the distance of the fixed stars from our Earth by aid of photography has been attended with success … Astronomical photography is hereby placed on a secure basis as an efficient and exact exponent of the highest form of astronomical science.61

As for Greenwich, aside from the sunspot research and participation in the Carte du Ciel there was also a new attempt to measure solar parallax using photography, this time of the asteroid Eros as it passed near the earth in October 1900. This attempt was organized by Simon Newcomb, who wrote in April 1900: It would seem that at the coming opposition of Eros, a better opportunity for determining solar parallax of the Sun by direct measurement will be offered than was ever before enjoyed … an additional consideration in favor of the photographic method is that photographic telescopes [Carte du Ciel instruments] well adapted for the pur-

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pose are actually in use at various favorably situated stations, and need only to be applied to this special problem in order to afford a solution.62

The Permanent Committee of the Carte du Ciel created a temporary ‘Eros Commission’ to plan micrometric, heliometric and photographic measurements of the positions of Eros against the backdrop of stars. Fifty-eight observatories participated.63 The telescope used at Greenwich (for both this and the Carte du Ciel) was a 13-inch refractor with a photographically-corrected enlarging lens. Though similar to De La Rue’s design for the transit photoheliographs, there were important differences in the optical correction of the enlarging lens and in the focusing mechanism, which employed a ‘guiding telescope’ attached to the outside of the instrument. Christie published Greenwich’s measure of solar parallax from Eros in 1907, giving a result of 8˝.800 ± 0˝.0044.64 Christie’s successor, H. Spencer Jones, carried out a similar photographic programme in 1930–1 when Eros passed even closer to the Earth. The result, 8˝.870, was reported to be accurate within 0˝.0001, or 9,000 miles, giving the most accurate measure of solar parallax ever obtained by an astrometric method.65 This work set the standard for the value of solar parallax until 1968, when the photographic measure was replaced by a new technique based on radar.

NOTES

The following abbreviations are used in the notes: DNB

Dictionary of National Biography, on CD-ROM (Oxford: Oxford University Press, 1995). MNRAS Monthly Notices of the Royal Astronomical Society. All references for the MNRAS and The Observatory have been extracted from the NASA Astrophysical Data Service and follow the conventions of that database. In particular, when listing the pages of an article in a footnote, only the first page number is given. Phil. Trans. Philosophical Transactions of the Royal Society of London. PRO Public Record Office, Kew, Surrey. RGO Royal Greenwich Observatory Archives, Cambridge University Library. ROE Royal Observatory, Edinburgh. RAS Royal Astronomical Society Library.

Introduction 1.

Maxwell’s 1871 Inaugural Lecture at Cambridge University, quoted in L. Campbell, The Life of James Clerk Maxwell (London: Macmillian, 1884), p 270. 2. A. Clerke, A Popular History of Astronomy During the Nineteenth Century, 4th edn (London: A. & C. Black, 1902), p. 280. 3. The context here is that the Admiralty had declined, against the Astronomer Royal’s wishes, to perform new longitude measures of the eastern coast of the United States. E. N. Swainson to the Chair of Board of Visitors to Greenwich, 13 June 1882, PRO ADM 190/14. 4. Clerke, A Popular History of Astronomy, p. 279. 5. My understanding of the ideology of the Great Exhibition follows that explored in J. Auerbach, The Great Exhibition of 1851: A Nation on Display (New Haven, CT: Yale University Press, 1999). 6. E. Renan, ‘What is a Nation?’ (1882), in G. Eley and R. Grigor (eds), Becoming National: A Reader (New York and Oxford: Oxford University Press, 1996), pp. 41–55. 7. Renan, ‘What is a Nation?’, p. 52. 8. On the empirical rhetoric of Humboldtian science, see S. F. Cannon, Science in Culture: The Early Victorian Period (New York: Science History Publications, 1978). 9. Clerk Maxwell, quoted in Campbell, The Life of James Clerk Maxwell, p 270. 10. The Graphic (London), 19 December 1874. 11. Anon., ‘The Transit of Venus, The Farmer’s Almanac, 72:48 (10 June 1876). 12. See for example Clerke, A Popular History of Astronomy. – 173 –

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Notes to pages 5–10

13. D. Judd, Someone Had Blundered: Calamities of the British Army in the Victorian Age (London: Arthur Barker, 1973). 14. The following deal mostly with the eighteenth-century transits: E. Maor, June 8, 2004: Venus in Transit (Princeton, NJ: Princeton University Press, 2000); D. Sellers, The Transit of Venus: The Quest to Find the True Distance of the Sun (Leeds: MagaVelda Press, 2001); W. Sheehan and J. Westfall, The Transits of Venus (Amherst, NY: Prometheus Books, 2004); H. Woolf, The Transits of Venus: A Study of Eighteenth-Century Science (Princeton, NJ: Princeton University Press, 1959). Woolf ’s is by far the most complete work on the transits of the eighteenth century. 15. Those exceptions include M. E. Chauvin, Hokuloa: The British 1874 Transit of Venus Expedition to Hawai’i (Honolulu, HI: Bishop Museum Press, 2004); F. Launay and P. D. Hingley, ‘Jules Janssen’s “Revolver Photographique” and its British Derivative, “The Janssen Slide”’, Journal of the History of Astronomy, 36:1 (2005), pp. 57–79; and Clerke’s discussion of the transit programme in A Popular History of Astronomy. 16. On the French programme, see J. Canales, ‘Photogenic Venus: The “Cinematographic Turn” and its Alternatives in Nineteenth-Century France’, Isis, 93 (2002), pp. 585–613. On the American programme, see S. J. Dick, ‘The American Transit of Venus Expeditions of 1882, Including San Antonio’, Bulletin of the American Astronomical Society, 27 (1995), p. 1331; S. J. Dick, Sky with Ocean Joined: The U.S. Naval Observatory, 1830– 2000 (New York: Cambridge University Press, 2002); S. J. Dick, W. Orchiston and T. Love, ‘Simon Newcomb, William Harkness and the Nineteenth-Century American Transit of Venus Expeditions’, Journal of the History of Astronomy, xxxix (1998), pp. 221– 55; W. Orchiston, T. Love and S. J. Dick, ‘Refining the Astronomical Unit: Queenstown and the 1874 Transit of Venus’, Journal of Astronomical History and Heritage, 3 (2000), pp. 23–44. On the German programme, see H. W. Duerbeck, ‘The Beginnings of German Governmental Sponsorship in Astronomy: The Solar Eclipse Expeditions of 1868 and the Venus Transit Expeditions of 1874 and 1882’, Astronomische Nachrichten Supplement, 324 (2003), p. 90; H. W. Duerbeck, ‘The German Expeditions of 1874 and 1882 to Observe the Transits of Venus: The Planning and the Execution of a Major Scientific Project’, Applied and Computational Harmonic Analysis, 21 (2004), pp. 57–97. On the Russian programme, see S. Werrett, ‘Transits and Transitions: Astronomy, Topography and Politics in the Russian Expedition to Observe the Transit of Venus’, Cahiers François Viète, 11–12 (2007), pp. 147–76. Note that issue 11–12 Cahiers François Viète is a special issue on the nineteenth-century transits of Venus. This is probably the most comprehensive source of recent research on the subject.

1 The Precedent 1.

2.

3.

E. Halley, ‘A New Method of Determining the Parallax of the Sun, or his Distance from the Earth’, Phil. Trans. Abridged, 6 (1713–23), p. 244–6. Transits of Mercury are not as suitable for measuring the sun’s distance simply because, with the planet being farther away, the parallactic effect would be smaller and thus more difficult to measure. For the role of parallax in the transit method, see Figure 1. B. Martin, ‘Dr Halley’s Dissertation on the Method of Determining the Parallax of the Sun by the Transit of Venus, June 6. 1761’, in B. Martin, Venus in the Sun (London, 1761), p. 5. Today the mean distance to the sun is referred to as the Astronomical Unit and is measured in kilometres. Astronomers of the eighteenth and nineteenth centuries referred to

Notes to pages 10–16

4.

5.

6. 7.

8. 9.

10.

11. 12. 13. 14.

15. 16.

175

the sun’s distance in terms of ‘solar parallax’ rather than miles or kilometres. The solar parallax is the apparent angular size of the Earth’s radius as seen from the sun, measured in seconds of arc. ‘Seconds of arc’ refers to the unit of measurement used by astronomers to designate positions of objects in the sky. This angular scale, derived from timekeeping, is defined by a circle divided into 24 hours, with each hour divided into 60 minutes, and each minute divided into 60 seconds. With this method, Halley said, the sun’s parallax may be discovered ‘… even to a small part of a second of time; and that without any other instruments than telescopes and good common clocks, and without any other qualifications in the observer than fidelity and diligence, with a little skill in astronomy’. Halley, ‘A New Method of Determining the Parallax of the Sun’, p. 244. From observations of Mars in opposition in 1672, J. D. Cassini calculated a distance of 87 million miles, Flamsteed a distance of 81 million miles, and Picard a distance of 41 million miles. See Woolf, The Transits of Venus, p. 14. Ibid.; Sellers, The Transit of Venus; Sheehan and Westfall, The Transits of Venus. G. B. Airy, ‘The Substance of a Lecture Delivered before the Society on the 8th of April, by the Astronomer Royal, “On the Means Which Will Be Available for Correcting the Measure of the Sun’s Distance, in the Next Twenty Five Years”’, MNRAS, 17 (1857), p. 208. W. Harkness, ‘Address by William Harkness’, Proceedings of the American Association for the Advancement of Science, Thirty-First Meeting (Montreal, August 1882), p. 77. One particular example illustrates how at that time ideas could spread in an informal and unorganized fashion across huge geographical regions. Delisle wanted to send a memoir describing the coming transits of Mercury and Venus to a Jesuit astronomer in Quebec, but if his letter was sent on the next ship bound for Quebec it would not get there in time. So he instead sent the memoir on a much swifter and more frequent ship to New York, putting it inside one addressed to the Governor of New York, and asking him to forward it ‘express overland’ to Quebec. This the Governor did, but not before having an English copy of the astronomical memoir made. One of these copies made it into the hands of Benjamin Franklin and Cadawallader Colden, who saw it as important and had fifty more copies made for American distribution. A separate announcement about the Mercury transits by Delisle, this time intended explicitly for public distribution, was sent all over the Continent, being sold at bookshops in Stockholm and Paris, at societies in the Hague, and so on. See Woolf, The Transits of Venus, pp. 43–4. In the Mars opposition method, which was also used later in the nineteenth century, the parallactic displacement of the planet with respect to certain stars is measured using two observations from the same location. One observation is made just after sunset and another just before sunrise, so the distance that the earth has rotated between observations provides the baseline. Woolf, The Transits of Venus, pp. 38–9. Ibid., p. 39. See p. 49 below. Council Minutes of the Royal Society of London, 1660–1800, 11 vols on 3 microfilms (Frederick, MD: University Publications of America, 1985), vol. 4, p. 235. Also quoted in Woolf, The Transits of Venus, p. 83. Ibid., p. 90. Ibid., p. 135.

176

Notes to pages 16–26

17. For a fictionalized account of Mason and Dixon’s transit of Venus expedition, including the attack by the French, see T. Pynchon, Mason and Dixon (New York: Henry Holt and Co., 1997). 18. R. A. Proctor, Transits of Venus, from the First Observed A.D. 1639 to the Transit of A.D. 2012 (London: Longmans, Green, 1874), p. 60. 19. Woolf, The Transits of Venus, p. 167. 20. Ibid., p. 192. 21. Ibid., p. 197. 22. Ibid., p. 189. 23. See T. S. Kuhn, The Structure of Scientific Revolutions (Chicago, IL: University of Chicago Press, 1962). 24. Woolf, The Transits of Venus, p. 3.

2 Big Science in Britain c. 1815–70 1.

2. 3. 4. 5. 6. 7. 8. 9.

10. 11. 12. 13. 14. 15. 16. 17.

18.

J. Herschel ‘Presidential Address’, Report on the Fifteenth Annual Meeting of the British Association for the Advancement of Science, cited in J. Cawood, ‘The Magnetic Crusade: Science and Politics in Early Victorian Britain’, Isis 70:4 (1979), pp. 492–518, on p. 516. J. H. Capshew and K. A. Rader, ‘Big Science: Price to the Present.’ Osiris, 2nd series, 7 (1992), pp. 2–25, on p. 20. For example see ibid. Quoted in Cawood, ‘The Magnetic Crusade’, p. 493. Ibid., p. 496. Ibid., p. 506. Ibid., p. 509. See Naval Estimates for1840–5, quoted in Cawood, ‘The Magnetic Crusade’, p. 517. Although Cawood points out that, for Sabine, some degree of success came when in 1851 the data was shown to reveal a correlation between the sunspot cycle and the periodicity of magnetic storms. Ibid., pp. 516–17. Ibid., p. 517. Ibid., p. 507. For a survey of the ‘awareness of crisis’ in science at the time, see P. Alter, The Reluctant Patron: Science and the State in Britain, 1850–1920 (Oxford: Berg, 1987), ch. 2. D. S. L. Cardwell, The Organisation of Science in England (London: Heinemann Educational, 1972), p. 70. Quoted in Alter, The Reluctant Patron, p. 221. Cardwell, The Organisation of Science in England; J. B. Poole and K. Andrews, The Government of Science in Britain (London: Weidenfeld and Nicolson, 1972). R. A. Proctor, Wages and Wants of Science-Workers (London: Smith, Elder, & Co., 1876), p. 104. The reason for this is not clear. It may be because the debate revolved around the application of science to industry, an application which was then not considered linked or linkable to military science. Or it may be that military expenditure on science was generally invisible even to amateur or civil scientific workers at the time. See E. Feuchtwanger and W. J. Philpott, ‘Civil-Military Relations in a Period without Major Wars, 1855–85’, in P. Smith (ed.), Government and the Armed Forces in Britain,

Notes to pages 26–30

19.

20. 21. 22. 23.

24. 25. 26. 27.

28. 29.

30. 31. 32. 33.

34.

35.

36.

177

1856–1990 (London: Hambledon Press, 1996), pp. 1–20; B. Ranft (ed.), Technical Change and British Naval Policy, 1860–1939 (London: Hodder and Stoughton, 1977). For example, in 1851 the Ordnance Department submitted an estimate of £97,654 for its ‘scientific branch’, out of a total budget of nearly £2.5 million. Hansard’s Parliamentary Debates, 115 (31 March 1851).Unfortunately the Admiralty’s expenditure on projects designated scientific has not been studied in any detail. Hansard’s Parliamentary Debates, 216 (1873–4). J. F. W. Herschel and D. Knight, Admiralty Manual of Scientific Enquiry, 2nd edn (1851; Folkstone: Dawsons, 1974), p. iv. See A. J. Meadows, Science and Controversy: A Biography of Sir Norman Lockyer (London: Macmillan, 1972). One study that deals directly with the importance of the ‘scientific servicemen’ in the early part of the nineteenth century is D. P. Miller, ‘The Revival of the Physical Sciences in Britain, 1815–1840’, Osiris, 2nd series, 2 (1986), pp. 107–34. Babbage’s views are discussed in Herschel and Knight, Admiralty Manual of Scientific Enquiry, p. 11. C. Babbage, Reflections on the Decline of Science in England, and on Some of Its Causes (1845; Shannon: Irish University Press, 1972), pp. 76–80. Cardwell, The Organisation of Science in England; Poole and K. Andrews, The Government of Science in Britain. R. MacLeod, Public Science and Public Policy in Victorian England (Aldershot: Variorum, 1996), p. vii; R. MacLeod, The ‘Creed of Science’ in Victorian England (Aldershot: Ashgate, 2000). W. J. Ashworth, ‘John Herschel, George Airy, and the Roaming Eye of the State’, History of Science, 36 (1998), pp. 152–78. D. R. Headrick, The Tools of Empire: Technology and European Imperialism in the Nineteenth Century (New York: Oxford University Press, 1981); D. R. Headrick, The Tentacles of Progress: Technology Transfer in the Age of Imperialism, 1850–1940 (New York: Oxford University Press, 1988). Cawood, ‘The Magnetic Crusade’, p. 518. Capshew and Rader, ‘Big Science’, p. 22. J. Tyndall, ‘Presidential Address’, British Association for the Advancement of Science Report, 44 (1874). A. Chapman, ‘Private Research and Public Duty: George Biddell Airy and the Search for Neptune’, Journal of the History of Astronomy, 19 (1988), pp. 121–39; A. Chapman, ‘George Biddell Airy, F.R.S. (1801–1892): A Centenary Commemoration’, Notes and Records of the Royal Society of London, 46:1 (1992), pp. 103–10. ‘Of the leading figures involved in geomagnetic activities, only Airy, the Astronomer Royal, who saw no purpose in the expedition, refused to join in the general enthusiasm, and even he agreed not to voice his opposition publicly, since Herschel had persuaded him that “a perfect harmony of ideas should subsist between men of science whenever application to Government is in question”’. Cawood, ‘The Magnetic Crusade’, p. 511. C. Stott, ‘The Greenwich Meridional Instruments (up to and Including the Airy Transit Circle)’, Vistas in Astronomy, 28 (1985), pp. 133–45; R. H. Tucker, ‘Greenwich Meridian Astronomy’, Vistas in Astronomy, 28 (1985), pp. 159–67. Even astronomers were beginning to adapt the chronometer to their needs for more precise longitude measures. One of the more successful results of the transit of Venus

178

37. 38.

39. 40. 41. 42. 43. 44. 45. 46. 47.

48. 49. 50.

51. 52.

53.

Notes to pages 30–5 expeditions involved a new evaluation of the precision attainable with marine chronometers. This is covered in Chapter 3. D. Howse, Greenwich Time and the Longitude (London: Philip Wilson, 1997). B. Morando, ‘The Golden Age of Celestial Mechanics’, in R. Taton and C. Wilson (eds), Planetary Astronomy from the Renaissance to the Rise of Astrophysics, The General History of Astronomy, vol. 2, part B (Cambridge: Cambridge University Press, 1995), pp. 211–39. J. A. Bennett, The Divided Circle: A History of Instruments for Astronomy, Navigation and Surveying (Oxford: Phiadon Christie’s, 1987), p. 165. Chapman, ‘Private Research and Public Duty’; Chapman, ‘George Biddell Airy, F.R.S.’. Ashworth, ‘John Herschel, George Airy’. S. Schaffer, ‘Astronomers Mark Time: Discipline and the Personal Equation’, Science in Context, 2 (1988), pp. 115–45. Ibid., p. 119. Quoted in R. W. Smith, ‘A National Observatory Transformed: Greenwich in the Nineteenth Century’, Journal of the History of Astronomy, 22 (1991), pp. 5–20, on p. 13. Ibid., p. 6. See for example D. G. Josefowicz, ‘Experience, Pedagogy, and the Study of Terrestrial Magnetism’, Perspectives on Science, 13:4 (2005), pp. 460–5. M. Croarken, ‘Astronomical Labourers: Maskelyne’s Assistants at the Royal Observatory, 1765–1811’, Notes and Records of the Royal Society of London, 57:3 (2003), pp. 285–98, on p. 294. Ibid., p. 292. Ibid., p. 287. The employee went on: ‘Eventually, of course, these juniors rose to positions of seniority, and they were able to introduce a more liberal attitude. Nowadays all the staff are positively encouraged to think about the work, and all routine calculations are performed painlessly by an electronic computer.’ Tucker, ‘Greenwich Meridian Astronomy’, p. 162. See also Stott, ‘The Greenwich Meridional Instruments’. Chapman, ‘George Biddell Airy, F.R.S.’. On the Challenger and other voyages of discovery as ‘in many ways analogous to the present-day space race’, see Poole and Andrews, The Government of Science in Britain, p. 9. A similar comparison is made in A. L. Rice, Voyages of Discovery: Three Centuries of Natural History Exploration (London: Scriptum Editions, 2000), p. 70. Anon., ‘The Astronomical Event of the Century’, The New York Times, 19 April 1874, p. 6.

3 Noble Science, Noble Nation 1. 2.

3.

Chapman, ‘Private Research and Public Duty’. C. H. Cotter, ‘The Early History of Ship Magnetism: The Airy-Scoresby Controversy’, Annals of Science, 34 (1977), pp. 589–99; A. Winters, ‘“Compasses All Awry”: The Iron Ship and the Ambiguities of Cultural Authority in Victorian Britain’, Victorian Studies (Autumn 1994), pp. 69–98. On Greenwich in the nineteenth century, see G. B. Airy, Autobiography of Sir George Biddell Airy, ed. W. Airy (Cambridge: Cambridge University Press, 1896); E. G. Forbes, A. J. Meadows and D. Howse, Greenwich Observatory: The Sotry of Britain’s Oldest Scientific Institution, the Royal Observatory at Greenwich and Herstmonceux, 1675–1975, 3

Notes to pages 35–42

4.

5.

6. 7.

8. 9.

10. 11. 12. 13. 14. 15. 16.

17. 18.

19. 20. 21.

22. 23.

179

vols (London: Taylor & Francis, 1975); Schaffer, Astronomers Mark Time’; Smith, ‘A National Observatory Transformed’; Chapman, ‘George Biddell Airy, F.R.S.’; Ashworth, ‘John Herschel, George Airy’. For more on the history of measuring the Astronomical Unit, as the sun’s distance is now known, see A. Van Helden, Measuring the Universe: Cosmic Dimensions from Aristarchus to Halley (Chicago, IL: University of Chicago Press, 1985); D. W. Hughes, ‘Six Stages in the History of the Astronomical Unit’, Journal of Astronomical History and Heritage, 4:1 (2001), pp. 15–28. In 1825, Johann Franz Encke produced a parallax of 8˝.577 using new longitude data; in 1868, Edward James Stone came up with a value of 8˝.91 ‘by simply interpreting strictly the language of the observers’. E. J. Stone, ‘A Rediscussion of the Observations of the Transit of Venus’, MNRAS, 28 (1868), p. 255, on p. 268. In 1891, Simon Newcomb produced a value of 8˝.79. Anon. ‘The Approaching Transit of Venus’, Edinburgh Review, 138 ( July 1873), pp. 144–65. R. Staley, ‘Conspiracies of Proof and Diversity of Judgement in Astronomy and Physics: On Physicists’ Attempts to Time Light’s Wings and Solve Astronomy’s Noblest Problems’, Cahiers François Viète, 11–12 (2007), pp. 83–97. Airy, ‘The Substance of a Lecture’, p. 208. In this method, the parallactic displacement of the planet with respect to stars is measured using two observations from the same location. One observation is made just after sunset and another just before sunrise, so the distance the earth has rotated provides the baseline. G. B. Airy to Normon R. Pogson, 1872, RGO/6-271 no. 512–14. Clerke, A Popular History of Astronomy, p. 279 (emphasis in original). DNB. Stone, ‘A Rediscussion of the Observations of the Transit of Venus’, p. 255. Ibid., p. 256. Ibid., p. 256. S. Newcomb, ‘Remarks on Mr. Stone’s Rediscussion of the Transit of Venus, 1769’, MNRAS, 29 (1868), p. 6; E. J. Stone, ‘A Reply to Mr. Newcomb’s Remarks on “Mr. Stone’s Rediscussion of the Transit of Venus”’, MNRAS, 29 (1868), p. 8. W. Lassell, ‘The Transit of Mercury, November 11, 1861’, MNRAS, 22:2 (1861), p. 38 (emphasis in original). J. Hartnup, ‘Observations on the Transit of Mercury Nov. 11 1861, made with the Equatoreal Refractor of the Liverpool Observatory’, MNRAS, 22 (1861), p. 41; J. Baxendall, ‘Observations of the Transit of Mercury, November 11, 1861’, MNRAS, 22 (1861), p. 42. The reports are printed in the December 1868 issue of the MNRAS. Cardwell, The Organisation of Science in England, p. 118. Quoted in Anon., ‘Science and Nature’, Scribner’s Monthly (December 1873), p. 173. Through 1873 and 1874, Scribner’s Monthly published excerpts from the Devonshire Commission’s reports. Cardwell, The Organisation of Science in England, p. 123. Cardwell (ibid., p. 124) states that the Devonshire Commission determined that the only State support for ‘middle-class’ science was the grant of £1,700 per annum for the examiners of London University, and a more generous allowance of £7,000 for the Scottish universities.

180

Notes to pages 42–8

24. Ibid., p. 126. See also Poole and Andrews, The Government of Science in Britain, p. 27. 25. G. Richards to G. B. Airy, 9 April 1869, RGO/6-268 no. 23–9. 26. Feuchtwanger and Philpott, ‘Civil-Military Relations in a Period without Major Wars’, p. 15. 27. A. Cowpe, ‘The Royal Navy and the Whitehead Torpedo’ in Ranft (ed.), Technical Change and British Naval Policy, pp. 23–36. 28. Hansard’s Parliamentary Debates, 198 (6 August 1869). 29. As George Forbes put it: ‘Pulkovo is like the palace of an astronomical autocrat who has but to will and men and money appear at his call to take the heavens by storm. Greenwich resembles the counting houses of some of our opulent city merchants, showing more brick than marble, but whose cellars are stored with the astronomical wealth of generations.’ Quoted in Ashworth, ‘John Herschel, George Airy’, p. 161 30. S. Werrett, ‘Transits and Transitions’. Russia established twenty-seven observation stations (complete with a telegraphic line connecting them to St Petersburg) in the recently-annexed territories of northern Siberia, thus giving Russia’s transit programme a more clearly practical purpose than existed in other participating countries. 31. M. Crosland, ‘Science and the Franco-Prussian War’, Social Studies of Science, 6 (1976), pp. 185–214, on p. 208. 32. G. Greenwood, ‘Washington Notes’, The New York Times, 19 February 1870. 33. Dick et al., ‘Simon Newcomb, William Harkness’; Dick, Sky with Ocean Joined. 34. The Irish Times (Dublin), 9 December 1874. 35. F. Diaz Covarrubias, Viaje De La Comision Astronomica Mexicana Al Japon (Mexico, 1876). For example: ‘El año de 1874 ha prescenciado un sucesso nuevo en nuestra historia. La Nacion Mexicana se ha hecho representar en el gran concurso cientifico a que dio lugar el ultimo transito de venus por el disco del sol …’, p. 7. 36. See p. 104 below. 37. Airy, ‘The Substance of a Lecture’, p. 216. 38. G. B. Airy, ‘On the Transit of Venus, 1882, December 6’, MNRAS, 24 (1864), p. 173; G. B. Airy, ‘On the Preparatory Arrangements which will be Necessary for Efficient Observation of the Transits of Venus in the Years 1874 and 1882’, MNRAS, 29:2 (1868), p. 33. 39. In addition to writing nineteen books and hundreds of articles, Proctor also founded the short-lived journal Knowledge: B. Lightman, ‘Knowledge Confronts Nature: Richard Proctor and Popular Science Periodicals’, in L. Henson et al. (eds), Culture and Science in the Nineteenth-Century Media (Aldershot: Ashgate, 2004), pp. 189–99. See also W. Noble, ‘Obituary: Richard Anthony Proctor’, Observatory, 11 (1888), pp. 366–8. 40. Anon., ‘Obituary: Richard Anthony Proctor’, MNRAS, 49 (1889), p. 164, on p. 164. 41. R. A. Proctor, ‘Note on the Transit of Venus in 1874; and an Exact Determination of Those Points on the Earth’s Surface at which Internal Contacts are most Accelerated and Retarded by Parallax. With an Addendum Referring to the Possibility of Determining the Solar Parallax by the same sort of Observations in 1874 as were made in 1769’, MNRAS, 29 (1869), p. 211, on p. 211. 42. R. A. Proctor, ‘The Transit of Venus in 1874’, MNRAS, 29 (1869), p. 306. 43. Anon., ‘The Approaching Transit of Venus’, Edinburgh Review, 138 ( July 1873), pp. 144–65, on p. 160. 44. Proctor, ‘Note on the Transit of Venus in 1874’, p. 221. 45. R. A. Proctor, ‘On Certain Important Conclusions Deducible from the Observations made on the Transit of Mercury at Greenwich, on November 5, 1868’, MNRAS, 30

Notes to pages 48–55

46. 47. 48. 49. 50.

51. 52. 53.

54. 55. 56.

57. 58.

59.

60. 61. 62. 63.

181

(1869), p. 46; Proctor, ‘Note on the Transit of Venus in 1874’; Proctor, ‘The Transit of Venus in 1874’; R. A. Proctor, ‘On the Comparative Clinging of the Limb of Venus to that of the Sun in the Transit of 1874 as Compared with that of 1882’, MNRAS, 29 (1869), p. 330; R. A. Proctor, ‘Note on the Transit of Venus in 1882’, MNRAS, 29 (1869), p. 332; R. A. Proctor, ‘On Spectroscopic Observations of the Transit of Venus in 1874’, MNRAS, 30 (1869), p. 37. R. A. Proctor to G. B. Airy, 27 February 1869, RGO/6-271 no. 528. Anon., ‘The Approaching Transit of Venus’, Spectator (London; 8 February 1873), pp. 175–6. Anon., ‘The Coming Transit of Venus’, The Times (London), 13 February 1873. Secretary of the Admiralty to G. B. Airy, 14 February 1873, RGO/6-267 no. 83. G. B. Airy, ‘Copy of a Letter from the Astronomer Royal to the Secretary of the Admiralty Expressing his Views on Certain Articles which had Appeared in the Public Newspapers’, MNRAS, 33:5 (1873), p. 270, on p. 272. Hansard’s Parliamentary Debates, 215 (25 March 1873). R. A. Proctor, ‘Remarks on a Letter from Sir G. B. Airy Respecting the Transit of Venus’, MNRAS, 33:5 (1873), p. 273, on p. 291. R. A. Proctor, ‘Note Accompanying a Chart of those Antarctic and Sub-Antarctic Regions which are Suitable for Observing the Transit of Venus in 1874’, MNRAS, 33:9 (1874), p. 533, on p. 533. G. B. Airy to R. A. Proctor, 6 March 1873, RGO/6-271 no 558. Capt. Evans to G. B. Airy, September 1873, RGO/6-267 no. 126–7. The debate is reviewed via a series of letters originally printed in The Times and republished in R. A. Proctor, W. De La Rue and E. B. Denison, ‘The Approaching Transit of Venus’, Astronomical Register, 12 (1874), pp. 39–43. Between March and June of 1873, Proctor published fifteen articles about the transit in MNRAS, 33. The events at the contentious Council meetings are covered in J. Browning et al., ‘Royal Astronomical Society’s Meetings’, Astronomical Register, 11 (1873), pp. 93–7; R. A. Proctor, ‘Correspondence – Late Events in the Royal Astronomical Society’, Astronomical Register, 11 (1873), pp. 181–4; R. A. Proctor and W. Noble, ‘Correspondence – Recent Events in the Astronomical Society’, Astronomical Register, 11 (1873), pp. 128–30; R. A. Proctor et. al., ‘The Royal Astronomical Society’s Meeting’, Astronomical Register, 11 (1873), pp. 120–3; R. A. Proctor, ‘Correspondence – The Annual Meeting of the Astronomical Society, and what took place thereat’, Astronomical Register, 11 (1873), pp. 97–100. For an account of Proctor’s career in the United States, see L. O. Saum, ‘The Proctor Interlude in St. Joseph and in America: Astronomy, Romance, and Tragedy’, American Studies International, 37:1 (1999), pp. 34–54. Anon., ‘On Mr. Proctor’s Lecture Tour’, The Nation, 16 April 1874, pp. 251–2. Hansard’s Parliamentary Debates, 219 (12 June 1874). Anon., ‘The Approaching Transit of Venus’, Edinburgh Review, 138 ( July 1873), pp. 144–65, on p. 164. Cardwell, The Organisation of Science in England, p. 64. Another case of the influence of national ideology on science can be found in the British resistance to the metric system in the decades after the Great Exhibition. See E. F. Cox, ‘The Metric System: A QuarterCentury of Acceptance’, Osiris, 13 (1958), pp. 358–79.

182

Notes to pages 55–63

64. On the rhetoric of internationalism in science, see MacLeod, The ‘Creed of Science’ in Victorian England, pp. 63–93. Also see R. Hutchins, ‘British University Observatories C1820–1939: Ideals and Resources’ (unpublished thesis, University of Oxford, 1999), esp. pp. 218–19. 65. The term ‘imagined community’ was coined by Benedict Anderson in B. R. Anderson, Imagined Communities: Reflections on the Origin and Spread of Nationalism (London: Verso, 1991). 66. N. Rich, The Age of Nationalism and Reform, 1850–1890, 2nd edn (New York: Norton, 1977), p. 44. 67. Anon., ‘The Astronomical Event of the Century’. 68. G. Forbes, ‘Science and Nature’, Scribner’s Monthly, 9:1 (1874), p. 261.

4 Inside Greenwich 1.

2. 3. 4. 5.

6. 7.

8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

They were, as Schaffer puts it, sites of ‘continuous surveillance’ rather than ‘heroic experimentation’. S. Schaffer, ‘Where Experiments End: Tabletop Trials in Victorian Astronomy’, in J. Z. Bushwald (ed.), Scientific Practice: Theories and Stories of Doing Physics (Chicago, IL: University of Chicago Press, 1995), pp. 257–99, on p. 279. G. B. Airy to A. Auwers, 27 April 1871, RGO/6-271 no. 887. A. D. B. D., ‘Obituary of George Lyon Tupman’, MNRAS, 83:4 (1923), p. 247. See also Figure 9 below, p. 89. Tupman is seated fourth from the left. Chapman, ‘George Biddell Airy, F.R.S.’, p. 107. A typical Airy note: ‘I should be pleased to have it understood as a rule (the rule to be notified to all principal observers), that every receipt of an instrument or part of an instrument and every delivery of an instrument or part of an instrument, be made known to me immediately by note on a separate piece of paper, written, as usual, with ample blank margin [signed Airy]’. Tupman’s Home Journal, 23 March 1873, RGO 56/56. L. Daston and P. Galison, ‘The Image of Objectivity’, Representations, 40 (1992), pp. 81–128. J. Tucker, Nature Exposed: Photography as Witness in Victorian Science (Baltimore, MD: Johns Hopkins University Press, 2005); H. Rothermel, ‘Images of the Sun: Warren De La Rue, George Biddell Airy and Celestial Photography’, British Journal for the History of Science, 26 (1993), pp. 137–69; J. Lankford, ‘Photography and the 19th-Century Transits of Venus’ Technology and Culture, 28:3 ( July 1987), pp. 648–57. W. A. Wiseman, The De La Rue Years, 1878–1910, 2 vols (London: Bridger & Kay / Gibbons, 1984–90), vol. 2, p. 242; DNB. E. C. Pickering, An Investigation in Stellar Photography Conducted at the Harvard College Observatory (Cambridge, MA: J. Wilson and Son, 1886), p. 180. W. De La Rue, ‘On the Total Solar Eclipse of July 18, 1860’, Phil. Trans., 152 (1862), pp. 333–416. Ibid., pp. 374, 407. Ibid., p. 412. Anon., ‘Obituary of Warren De La Rue’, MNRAS, 50 (1890), p. 155. W. De La Rue, ‘On the Observations of the Transits of Venus by Means of Photography’, MNRAS, 29 (1868), p. 48, on pp. 50–1, 53. See p. 124 below. Reprinted in Rothermel, ‘Images of the Sun’. ‘Visitors of the Royal Observatory at Greenwich Minute Book’, PRO ADM 190/4.

Notes to pages 63–7

183

18. W. De La Rue to G. B. Airy, 14 March 1870, RGO/6-271 no. 152. 19. For more on the origins of the Kew photoheliograph, see Rothermel, ‘Images of the Sun’, pp. 151–3. 20. Secretary of the Admiralty to G. B. Airy, 21 June 1871, RGO/6-267 no. 57. 21. G. B. Airy to W. De La Rue, 7 July 1871, RGO/6-271 no. 178 (emphasis in original). 22. De La Rue, ‘On the Total Solar Eclipse’, p. 370. In the 1860 eclipse report, De La Rue wrote that the ‘measurements could not generally be made nearer than 0.001 inch, equal to 0˝.5 …’ and the final results were reported to within half a second of arc. The Kew sunspot measurement report states that ‘all measurements were made with the greatest possible care by means of the Kathetometer [De La Rue’s radial micrometer] of the Observatory, which reads to 1/1000 of an inch’. W. De La Rue, B. Lowey and B. Stewart, ‘Researches on Solar Physics. Heliographical Positions and Areas of Sun-Spots Observed with the Kew Photoheliograph during the Years 1862 and 1863’, Phil. Trans., 169 (1868), pp. 2–110, on p. 18. 23. W. De La Rue to G. B. Airy, 11 July 1871, RGO/6-271 no. 180 (emphasis in original; the reading of the bracketed words is unsure). 24. G. B. Airy to Secretary of the Admiralty, 27 July 1871, RGO/6-267 no. 63–5. 25. ‘De La Rue thinks that it’s possible to measure distance of centres of Venus and the sun with certainty to within 0˝.5 including all sources of error. But the chief advantage would be in case of cloud at the time of ingress or egress’. Ibid. See also W. De La Rue to G. B. Airy, 14 March 1870, RGO/6-271 no. 152. 26. G. B. Airy to W. De La Rue, 16 March 1870, RGO-6/271 no. 156. 27. Anon., ‘The Coming Transit of Venus’, Nature (4 January 1872), p. 178. 28. Most writing on the history of photography has not dealt with the wet-plate era. This is especially true of the influential cultural historians from the early 1980s, such as John Berger and Roland Barthes, who have theorized about the effect of the rise of photography on society, including modes of authority and concepts of objectivity and subjectivity. Berger most famously argued that in the early twentieth century photographs ‘replaced the world as immediate testimony’. Quoted in Rothermel, ‘Images of the Sun’, p. 138. 29. S. Newcomb and G. W. Hill, Papers Relating to the Transit of Venus in 1874 (Washington, DC: Transit of Venus Commission, 1872), p. 25. 30. G. B. Airy to Warren De La Rue, 16 September 1871, RGO/6-271 no. 192. 31. The clarity of the limb would obviously affect the accuracy and precision of the eye-observations as well, but, in that case, by bearing on the ability of an observer to determine the moment of contact between the edge of Venus and the edge of the sun. Lindsay and Gill considered the risk of solar flares or protuberances interfering with observations of contact to be a serious drawback to the contact method. J. L. L. Crawford and D. Gill, ‘On Lord Lindsay’s Preparations for Observations of the Transit of Venus, 1874’, MNRAS, 33 (1872), p. 34. 32. J. N. Lockyer, ‘On Spectroscopic Observations of the Sun’, Phil. Trans., 159 (1869), pp. 425–44, on p. 430. 33. De La Rue, ‘On the Total Solar Eclipse’, p. 374. 34. J. Lankford, ‘The Impact of Photography on Astronomy’, in O. Gingerich (ed.), Astrophysics and Twentieth-Century Astronomy to 1950, The General History of Astronomy, vol. 4 (Cambridge: Cambridge University Press, 1984), pp. 16–39, on p. 17. 35. Admiral Sands to L. M Rutherfurd, 19 January 1872, in Newcomb and Hill, Papers Relating to the Transit of Venus in 1874.

184

Notes to pages 68–78

36. L. M. Rutherfurd to Admiral Sands, 23 January 1872, in Newcomb and Hill, Papers Relating to the Transit of Venus in 1874. 37. De La Rue et al., ‘Researches on Solar Physics’. 38. ‘On the Application of Photography to the Observation of the Transit of Venus’, in Newcomb and Hill, Papers Relating to the Transit of Venus in 1874, p. 23 (emphasis in original). 39. W. De La Rue to G. B. Airy, May 1872, RGO/6-271 no. 203. 40. Lord Lindsay, ‘On Photograpic Irradiation’, MNRAS, 32 (1872), p. 313. 41. Ibid., p. 317 (emphasis in original). 42. J. R. Ryan, Picturing Empire: Photography and the Visualization of the British Empire (London: Reaktion, 1997), p. 78. 43. DNB. 44. W. d. W. Abney, Emulsion Processes in Photography (London: Piper & Carter, 1878), p. 74. For a detailed description of Abney’s process, see also W. d. W. Abney, ‘Photography in the Transit of Venus’, MNRAS, 34 (1875), p. 275. 45. G. B. Airy to W. De La Rue, 12 March 1870, RGO/6-271 no. 151. 46. De La Rue, ‘On the Total Solar Eclipse’, p. 368. 47. W. De La Rue to G. B. Airy, September 1871, RGO/6-271 no. 193–5. 48. G. L. Tupman to G. B. Airy, 8 November 1873, RGO/6-270 no. 120. 49. W. Christie to W. De La Rue, 5 March 1874, RGO/6-271 no. 233. The quote continued: ‘The sensitiveness seems greater than for wet plates, for even with the present small altitude of the sun we are obliged to use the stop with a slip of 0.1 inch and all the pictures lately … have been overexposed’. See also W. De La Rue to G. B. Airy, 7 March 1874, RGO/6-271 no. 237. 50. J. Lankford (ed.), History of Astronomy: An Encyclopedia (New York: Garland Publishing, 1997). 51. S. Newcomb (ed.), Observations of the Transit of Venus, December 8–9, 1874. Made and Reduced under the Direction of the Commission Created by Congress (Washington, DC: Transit of Venus Commission, 1880), p. 11. 52. G. Forbes REF MISSING 53. Crawford and Gill, ‘On Lord Lindsay’s Preparations’, p. 34. 54. G. B. Airy to A. Auwers, 27 April 1871, RGO/6-271 no. 887. 55. Canales, ‘Photogenic Venus’; Launay and Hingley, ‘Jules Janssen’s “Revolver Photographique”’. 56. W. De La Rue to G. B. Airy, 17 March 1873, RGO/6-271 no. 219. 57. G. B. Airy to W. De La Rue, 19 March 1873, RGO-6/271 no. 222. 58. For a good introduction to the philosophical issues, see ‘Models in Science’ in the Stanford Encyclopedia of Philosophy at http://plato.stanford.edu. 59. John Bevis, one of the members of the Royal Society’s Transit Committee, suggested using a mechanical simulator, in which a small artificial Venus could be observed moving across an artificial sun, in preparing and training observers for the transit. Council Minutes of the Royal Society, 30 November 1767. A reconstruction of the Martin model was built in 2004 at the Museum of the History of Science in Oxford. 60. See Schaffer, ‘Where Experiments End’. 61. Anon., ‘Artificial Transit of Venus at the Royal Observatory’, The Graphic (London), 17 December 1874.

Notes to pages 78–85

185

62. According to the letter’s conclusion, the Russians also considered the models ‘quite necessary to secure their success’. A. Auwers to G. B. Airy, 31 August 1872, RGO/6-271 no. 894. 63. Unknown author, October 1873, RGO/6-277 no. 632. 64. The American model is described in S. Newcomb, Popular Astronomy, 2nd edn (London: Macmillan, 1910). The French models are described in C. Wolf and C. L. F. André, ‘Recherches sur les apparences singulières qui ont souvent accompagnés l’observation des contacts de Mercure et de Vénus avec le bord du soleil’, Recueil de mémoires, rapports et documents relatifs a l’observation du passage de Vénus sur le soleil, 9 vols (Paris: Didot frères Gauthier-Villars, 1876–90), vol. 1, part 2. 65. C. O. Browne to W. Christie, 4 April 1874, RGO/6-277 no. 698. 66. For more on Lockyer’s experiments, see Schaffer, ‘Where Experiments End’. 67. G. B. Airy to G. L. Tupman, 19 November 1873, RGO/6-270 no. 126 (emphasis in original). 68. DNB. 69. The results were written up in an unpublished pamphlet: G. Forbes, ‘The Appearances Presented by the Model Transit of Venus, Mounted at the Royal Observatory, With a Cloudy Sky’, 25 October 1873, RGO/6-277 no. 665. 70. Anon., ‘Preparations for Observing the Transit of Venus’, MNRAS, 34 (1874), p. 186, on p. 188. 71. Ibid., p. 188. 72. G.B. Airy to G. Forbes, 1 November 1873, RGO/6-277 no. 678. 73. G. Forbes, ‘The Coming Transit of Venus: IV’, Nature (14 May 1874), pp. 27–30, on p. 28. 74. B. E. Schaefer, ‘The Transit of Venus and the Notorious Black Drop’, Bulletin of the American Astronomical Society, 197th meeting (2000), 1.03. 75. G. L. Tupman to G. B. Airy, 10 December 1873, RGO/6-270 no. 142. 76. G. L. Tupman to G. B. Airy, 15 September 1872, RGO/6-270 no. 31–3. 77. G. L. Tupman to G. B. Airy, 29 November 1873, RGO/6-270 no. 136. 78. G. B. Airy to Secretary of the Admiralty, 21 March 1873, RGO/6-267 no. 95–104 (the reading of the bracketed letters is unsure). 79. Forbes, ‘The Coming Transit of Venus: IV’. 80. G. B. Airy to G. Forbes, 1 November 1873, RGO/6-277 no. 678. 81. D. Gill to G. B. Airy, 6 June 1874, RGO/6-271 no. 385. 82. See pp. 29–30 above. 83. Schaffer, ‘Astronomers Mark Time’, pp. 125–6. 84. C. Wolf and C. L. F. André, ‘Recherches sur les apparences singulières qui ont souvent accompagnés l’ observation des contacts de Mercure et de Vénus avec le bord du soleil’, Annales de l’Observatoire de Paris, 10 (1874), pp. 131–49. 85. C. Wolf, ‘Recherches sur l’equation personnelle dans les observations de passages, sa determination absolue, ses lois et son origine’, Annales de l’Observatoire de Paris, 8 (1866), pp. 153–208, on p. 169. For an earlier training model, see C. R. Chary, ‘On the Determination of Personal Equation by Observations of the Projected Image of the Sun, Letter from C. Ragoonatha Chary, of the Madras Observatory, to Captain W. S. Jacob’, MNRAS, 19 (1859), p. 337. See also O. Struve, ‘On the Measures Made on Artificial Double Stars, and on the Observations of the Eclipse of 1851’, MNRAS, 20 (1860), p. 341.

186

Notes to pages 85–92

86. See, for example, G. B. Airy, ‘Remarks upon Certain Cases of Personal Equation’, MNRAS, 16 (1855), p. 6. 87. See W. H. M. Christie, ‘Description of the Personal Equation Machine of the Royal Observatory, Greenwich’, MNRAS, 48 (1887), p. 1. 88. See, for example, Dun Echt Observatory, ‘The Transit of Venus Expedition, Part II’, Dun Echt Observatory Publications, 3 (1885), ch. 5: ‘Determination of the Difference of Personal Equation in Finding the Time between Lieutenant Neate, Mr. Burton, and Mr. Gill’, pp. 122–9; ch. 7: ‘Determination of the Difference of Personal Equation between Dr. Pechule and Mr. Gill in Finding the Time with their Respective Instruments at Belmont, and in Recording Telegraphic Signals’, pp. 149–54. 89. The official report states: ‘The practice with the model … demonstrated that there was no material difference between the different observers’ appreciation of the exact moment of contact …’. G. B. Airy (ed.), Account of Observations of the Transit of Venus, 1874, December 8, Made under the Authority of the British Government, and of the Reduction of the Observations (London: Her Majesty’s Stationery Office, 1881), p. 56. In contrast, Canales reports that in France Wolf and André rejected any ideas of physiological effects of irradiation, and concluded from their own experiments that telescopic differences were to blame. See J. Canales, ‘Sensational Differences: The Case of the Transit of Venus’, Cahiers François Viète, 11–12 (2006), pp. 15–40, on p. 20. 90. This use of ‘impersonality’, describing more accurately what is often referred to as ‘objectivity’ in science, is from T. M. Porter, ‘Quantification and the Accounting Ideal in Science’, Social Studies of Science, 22 (1992), pp. 633–52. 91. Newcomb and Hill, Papers Relating to the Transit of Venus in 1874, pp. 14–25. 92. Chapman, ‘Private Research and Public Duty’, p. 135. 93. Smith, ‘A National Observatory Transformed’, p. 5 (emphasis in original). 94. Chapman, ‘Private Research and Public Duty’, p. 135. 95. Canales, ‘Sensational Differences’, p. 25. 96. M. S. Drower, Flinders Petrie: A Life, 2nd edn (Madison, WI: University of Wisconsin Press, 1995), p. 28. 97. Smyth (1870), quoted in S. Schaffer, ‘Metrology, Metrication, and Victorian Values’, in B. Lightman (ed.), Victorian Science in Context (Chicago, IL: University of Chicago Press, 1997), pp. 438–74, on pp. 455–6.

5 The Expeditions 1. 2. 3.

4. 5. 6. 7.

Anon., ‘The Transit of Venus’, The Times (London), 9 December 1874, p. 9. T. Hardy, Two on a Tower (1882; London: Penguin Books, 1999), p. 245. See, for example, Z. Baber, The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India, SUNY Series in Science, Technology, and Society (Albany, NY: State University of New York Press, 1996); D. Kumar, Science and the Raj: 1857–1905 (Oxford: Oxford University Press, 1995); R. M. MacLeod and D. Kumar, Technology and the Raj: Western Technology and Technical Transfers to India 1700–1947 (New Delhi: Sage, 1995). S. Goodfellow, quoted in Baber, The Science of Empire, p. 185. Punch, or The London Charivari, 19 December 1874. Anon., ‘The Transit of Venus’, The Times (London), 9 December 1874, p. 9. Anon., ‘The Otago Institute Annual Meeting, President’s Address’, The Otago Guardian (Otago, New Zealand), 2 February 1875.

Notes to pages 93–100 8. 9. 10.

11. 12.

13.

14.

15. 16.

17. 18. 19.

20. 21. 22. 23. 24. 25. 26.

27. 28. 29.

187

C. R. Chary, The Transit of Venus: A Discourse (Madras: n.p., [1874]), CUL RGO/6281, pp. 9, 10, 18. Ibid., p. i. C. R. Chary, Address Delivered by C. Ragoonatha Chary, F.R.A.S., at Pacheappah’s Hall, Madras, on 13th April 1874, to a Large Meeting of Native Gentlemen (Madras: Foster Press, 1874). Chary, The Transit of Venus, p. 21. After asking not to be sent to a proposed station at Peshawar, Pogson told Airy ‘I should much prefer to do your bidding here, with the well mounted trusty tools I am used to, and without the terribly unwelcome interruption of another “Expedition”. Tennant is quite welcome to the honour and glory derivable from all expeditions’. N. R. Pogson to G. B. Airy, 4 June 1873, RGO/6-271 no. 515–16 (emphasis in original). In the end, Tennant did take over the only official British station, managing the photographic operations at Roorkee. For detailed accounts of some of the other stations, see M. E. Chauvin, ‘Astronomy in the Sandwich Islands: The 1874 Transit of Venus’, Hawaiian Journal of History, 27 (1993), pp. 185–225; Chauvin, Hokuloa; S. J. Perry, Notes of a Voyage to Kerguelen Island to Observe the Transit of Venus, December 8, 1874, reprinted from Month and Catholic Review (London: H. King, 1876). A. S.-K. Pang, ‘The Social Event of the Season: Solar Eclipse Expeditions and Victorian Culture’, Isis, 84 (1993), pp. 252–77, on p. 277; A. S.-K. Pang, Empire and the Sun: Victorian Solar Eclipse Expeditions (Stanford, CA: Stanford University Press, 2002). C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. In his letters to Airy, Browne also discusses a private expedition run by Colonel and Mrs Campbell, which established camp at Suez. Their observations were not included in the data from Egypt. C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. Ryan, Picturing Empire, p. 15. W. d. W. Abney, Thebes and its Five Greater Temples. Illustrated with Forty Large Permanent Photographs by the Author (London: Sampston Low, Marston, Searle and Rivington, 1876). C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. Ibid. Ibid. Pang, ‘The Social Event of the Season. H. J. Schonfield, The Suez Canal in Peace and War (Coral Gables, FL: University of Miami Press, 1969). M. Badrawi, Isma’il Sidqi (1875–1950): Pragmatism and Vision in Twentieth-Century Egypt (Richmond, Surrey: Curzon Press, 1996), pp. 183–6. Apparently both methods of telling time were in use. Most of the country still used apparent solar time, but mean solar time was making inroads. ‘Watches’, wrote Browne, ‘are ill used by constant attempts to force them to agree with a gun in Cairo which the Sun itself fires at noon’. C. O. Browne to G. B. Airy, October–December 1874, RGO/6271 no. 756–822. Anon., ‘Death of Mr Charles Lambert’, The Hawaiian Gazette (Honolulu), 2 December 1874. A full history of this expedition is given in Chauvin, Hokuloa. Fairfax to Secretary of the Admiralty, 11 January 1875, RGO/6-267 no. 391–413. C. O. Browne to G. B. Airy, 12 November 1874, RGO/6-271 no. 785–9.

188

Notes to pages 100–10

30. Ibid. 31. G. B. Airy, ‘Report by the Astronomer Royal on the 56th Annual General Meeting’, MNRAS, 36:4 (1876), p. 178. 32. Eight are listed in the official report. Airy (ed.), Account of Observations of the Transit of Venus, pp. 263–5. 33. C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. 34. Airy, ‘The Substance of a Lecture’, p. 216. 35. See pp. 29–30 above. 36. For the chronometer runs between Greenwich and Pulkovo in 1843, for example, see Forbes et al., Greenwich Observatory, vol. 2, p. 117. 37. G. B. Airy, ‘On the Preparations to be made for Observation of the Transit of Venus, December 6, 1882’, MNRAS, 40 (1880), p. 381, on p. 382. 38. Perry, Notes of a Voyage to Kerguelen Island, p. 29. 39. D. Gill, ‘Transit of Venus, 1874’, Dun Echt Correspondence, ROE, 26.185. 40. Howse, Greenwich Time and the Longitude. 41. Dun Echt Observatory, ‘The Transit of Venus Expedition, Part II’, pp. 9–10. 42. Ibid., p. 23 (emphasis in original). 43. D. Gill, ‘Transit of Venus, 1874’, Dun Echt Correspondence, ROE, 26.185. 44. ‘Secretary to the Board of the Eastern Telegraph Company Minute Book Number 2, 1874’, Porthcurno Telegraph Museum, Cornwall. The interruption of traffic on four occasions is recorded on p. 178. 45. For a general history of the Eastern Telegraph Company (which became Cable and Wireless) and submarine telegraphy, see H. Barty-King, Girdle Round the Earth: The Story of Cable and Wireless and its Predecessors (London: William Heinemann, 1979). For the history of Porthcurno station, see D. Cleaver, A History of Porthcurno (n.p.: for the author, 1953); J. E. Packer, ‘Gateway to Empire’, paper given at the Royal Institution: Centre for the History of Science and Technology, Porthcurno Museum (1997), PK Technical Library 1.4.34. 46. Airy (ed.), Account of Observations of the Transit of Venus, p. 246. 47. Ibid., p. 266. 48. Browne also had a hand in designing the more sensitive recorder coil. Notes on the progress of the experiments from February 1873 through early 1874 are in ‘Copy of Spratt Diary’, 1871–4, Porthcurno Telegraph Museum, Cornwall. The modified recorder is described in Airy (ed.), Account of Observations of the Transit of Venus, pp. 267, 268. 49. T. Bell, ‘The “American Method”: The Nineteenth-Century Telegraphic Revolution in Finding Longitude’, paper given at the Institute of Electrical and Electronics Engineers Conference on the History of Telecommunications (St John’s, Newfoundland, 2001). See also I. Bartky, Selling the True Time: Nineteenth-Century Timekeeping in America (Stanford, CA: Stanford University Press, 2000), p. 312. 50. Anon. to W. Ansell Esq, 4 November 1874, Malta Letter Book, 1873–6, Porthcurno Telegraph Museum, Cornwall. 51. C. O. Browne, ‘On the Determination of the Longitude of Cairo from Greenwich by the Exchange of Telegraph-Signals’, Philosophical Magazine (6 May 1876). 52. Airy (ed.), Account of Observations of the Transit of Venus, p. 269. 53. As described by Perry, see p. 103 above. 54. C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. 55. Airy (ed.), Account of Observations of the Transit of Venus, pp. 42–4. 56. Ibid., p. 37.

Notes to pages 110–21

189

57. Quoted in Anon., ‘The Transit of Venus’, The Times (London), 9 December 1874, p. 9 (the reading of the bracketed word is unsure). 58. H. C. Russell, Observations of the Transit of Venus, 9 December, 1874: Made at Stations in New South Wales (Sydney: Sydney Observatory Publications, 1892), p. xiv (emphasis in original). 59. J. F. Tennant, Report on the Preparations for, and Observations of the Transit of Venus: As Seen at Roorkee and Lahore, on December 8, 1874 (Calcutta: Office of Government Printing, 1877), p. 24. 60. C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822. 61. See the section ‘On the Frauds of Observers – Of Cooking’ in Babbage, Reflections on the Decline of Science in England, pp. 174–82. 62. E. Richards, ‘Redrawing the Boundaries: Darwinian Science and Victorian Women Intellectuals’, in B. Lightman (ed.), Victorian Science in Context, pp. 119–43. 63. Babbage, Reflections on the Decline of Science in England, p. 182. 64. C. O. Browne to G. B. Airy, October–December 1874, RGO/6-271 no. 756–822 (emphasis in original). 65. Ibid. 66. Ibid. 67. ‘The New York Herald sent out one of their special scientific correspondents to Nagasaki, Japan, in reference to the Transits of Venus. He duly telegraphed the results of his observation, and it was retelegraphed tonight from New York in an utterly incomprehensible shape. No human being could translate the original, but as a curiosity in its way as a specimen of either Japanese or American telegraphy, I send you a copy verbatim et literatim: “Day cloudy, but obtained second contact well. Two observers. First and third contacts through clouds and doubtful. 1.50 miraometric measures of cusps, separation of limbs and diameter of Venus 31 meridian transits, both limbs, sun, and Venus 18 micrometric measures; for a difference of declination of limbs at meridian about 60. Good photographs. Ends threatening rain. Telegraph of longitude with plad Woodstock; in November. All well.”’. The Irish Times (Dublin), 10 December 1874 (emphasis in original). 68. The New Zealand Herald (Auckland), 3 December 1874. 69. The North China Daily News (Shanghai), 9 December 1874. 70. Anon., ‘Observation of the Transit’, The Pioneer (Allahabad), 8 December 1874. 71. The North China Daily News (Shanghai), 10 December 1874. 72. ‘The Transit of Venus’, The Times (London), 9 December 1874, p. 9. 73. Renan, ‘What is a Nation?’. 74. Recall that it was not only the newspapers that held up the transit as a prime example of a programme that deserved government funding. Both George Airy (‘The Endowment of Research’, Observatory, 4 (1881), pp. 87–9) and Richard Proctor (The Wages and Wants of Science-Workers) also cited the transit programme in the same way.

6 The Outcome 1. 2. 3.

G. B. Airy, ‘Copy of Telegrams Sent to the Undermentioned’, 8 December 1874, RGO/6271 no. 43–4. Daily News (London), 19 January 1875. Chapman, ‘George Biddell Airy, F.R.S.’, p. 105.

190 4. 5. 6. 7.

8. 9. 10.

11.

12. 13. 14. 15.

16.

17. 18.

Notes to pages 122–6 G. B. Airy, ‘On the Method to be used in Reducing the Observations of the Transit of Venus 1874, December 8’, MNRAS, 35 (March 1875), p. 277. Ibid., p. 288. T. Hornsby, ‘The Quantity of the Sun’s Parallax, as Deduced from the Observations of the Transit of Venus, on June 3, 1769’, Phil. Trans., 61 (1771), 574–7, on p. 579. The method of least squares is a statistical tool for finding the ‘best fit’ for a line through a set of points, providing a way of expressing the ‘most probable’ true result for a series of measurements. S. M. Stigler, The History of Statistics: The Measurement of Uncertainty Before 1900 (Cambridge, MA: Belknap Press of Harvard University Press, 1986); F. Schmeidler, ‘Astronomy and the Theory of Errors: From the Method of Averages to the Method of Least Squares’, in Taton and Wilson (eds), Planetary Astronomy from the Renaissance to the Rise of Astrophysics, pp. 198–207. The method is seen by some historians as a crucial element of a ‘probabilistic revolution’ that occurred throughout the natural and social sciences from 1800 to 1930. For discussion of the idea of a ‘probabilistic revolution’, both pro and con, see L. Krüger, L. J. Daston and M. Heidelberger (eds), The Probabilistic Revolution, 2 vols (Cambridge, MA: MIT Press, 1987). Airy, ‘On the Method to be used in Reducing the Observations’, p. 278. Stigler, The History of Statistics, p. 4. Z. G. Swijtink, ‘The Objectification of Observation: Measurement and Statistical Methods in the Nineteenth Century’, in Krüger et al. (eds), The Probabilistic Revolution, vol. 1, pp. 261–85, on p. 261. A report may say 3 ± 0.3, meaning that, assuming there are no systematic errors, it is an even bet that the true value is between 2.7 and 3.3 and that the most probable value is 3. See ibid. The Graphic (London), 17 December 1874. G. B. Airy to W. De La Rue, 16 January 1875, RGO/6-271 no. 242. Discussed on p. 67 above. On Airy’s transit circle, see p. 29 above. J. A. Bennett, ‘George Biddell Airy and Horology’, Annals of Science, 37 (1980), pp. 269–85; Bennett, The Divided Circle; Chapman, ‘George Biddell Airy, F.R.S.’; Forbes et al., Greenwich Observatory. Though no image of the instrument survives, Airy gave a detailed description of its construction. The instrument was made of two microscopes, separated by about 11.5 inches, both installed facing downwards into a rigid metal bar. The bar was set into a frame attached by 3-inch high pillars to a base plate about 24 inches wide and 7 inches long. The bar could slide horizontally within the frame. There were two rectangular openings cut into the base plate, through which light can be directed so that transparent objects could be placed on top and viewed through one of the two microscopes. Set into one of these openings was an etched-glass millimetre scale. The glass negative to be measured was placed over the other opening. The negative plates would be set into a circular frame so that they could be rotated once they had been placed in the instrument. Note that this rotating plate only allowed the points to be measured to be centred under the microscopes. In De La Rue’s instrument, the rotating plate was used in establishing an arc representing the limb of the sun on the plate. Measures of distances would then be made between arcs rather than, as in Airy’s instrument, between points. Airy, ‘Report by the Astronomer Royal’. Lewis M. Rutherfurd to Admiral Sands, 23 January 1872. In Newcomb and Hill, Papers Relating to the Transit of Venus in 1874. Anon., ‘Obituary of Warren De La Rue’.

Notes to pages 126–32

191

19. R. A. Proctor, ‘Photography in the Transit of Venus’, MNRAS, 35 (1875), p. 379. 20. For a discussion of the irradiation problem, see pp. 70–1 above. 21. J. L. L. Crawford and A. C. Ranyard, ‘Photographic Irradiation in Over-Exposed Plates’, MNRAS, 32 (1872), p. 313. 22. W. de W. Abney, ‘Photography in the Transit of Venus’, MNRAS, 35 (1875), p. 309, on p. 309. 23. W. H. M. Christie, ‘Note on the Determination of the Scale in Photographs of the Transit of Venus’, MNRAS, 35 (1875), p. 347, on p. 347. 24. Ibid. See also W. H. M. Christie, ‘Differences of Irradiation for Venus & Sun’, undated, RGO/6-272 no. 758. 25. G. B. Airy, 23 August 1875, RGO/6-272 no. 755. 26. G. B. Airy to G. Tupman, 16 June 1875, RGO/6-270 no. 272. 27. In Bradley Schaefer’s discussion of the appearances reported at contact, he argues that it would have been impossible for observers to have seen any light refracting through the atmosphere. See Schaefer, ‘The Transit of Venus and the Notorious Black Drop’. 28. G. L. Tupman to G. B. Airy, 31 July 1875, RGO/6-272 no. 660. 29. G. Browne to W. Christie, 4 April 1874, RGO/6-277 no. 698. 30. G. L. Tupman to G. B. Airy, 31 July 1875, RGO/6-272 no. 660. 31. Russell, Observations of the Transit of Venus, p. xii. 32. This appeared in the fourth edition of Proctor’s Transits of Venus (London: Longmans, Green, 1882). 33. E. J. Stone, ‘On Some Phenomena of the Internal Contacts Common to the Transits of Venus, Observed in 1769 and 1874, and Some Remarks Thereon’, MNRAS, 37 (1876), p. 45. 34. G. L. Tupman, ‘On the Mean Solar Parallax as Derived from the Observations of the Transit of Venus, 1874’, MNRAS, 38 (1878), p. 429, on p. 447. 35. G. B. Airy to Hoffman, 6 October 1873, RGO/6-277 no. 635; G. B Airy to Secretary of the Admiralty, 21 March 1873, RGO/6-267 no. 95–104. 36. Stone, ‘On Some Phenomena of the Internal Contacts’. 37. See p. 161 below. 38. Secretary of the Admiralty to G. B. Airy, 9 May 1876, RGO/6-267 no. 475. 39. G. B. Airy to Secretary of the Admiralty, 16 February 1876, RGO/6-267 no. 461–9. 40. G. B. Airy to Secretary of the Admiralty, 13 May 1876, RGO/6-267 no. 480–2. 41. Rice, Voyages of Discovery, p. 296. Also see: E. Linklater, The Voyage of the Challenger (London: J. Murray, 1972); Cotter, ‘The Early History of Ship Magnetism’; Winters, ‘“Compasses All Awry”’; E. V. Brunton, The Challenger Expedition, 1872–1876: A Visual Index (London: Natural History Museum, 1994); G. S. Ritchie, Challenger: The Life of a Survey Ship (London: Hollis & Carter, 1957). 42. MacLeod, Public Science and Public Policy in Victorian England, ‘Science and the Treasury: Principles, Personalities and Policies, 1870–85’, pp. 115–72. 43. See the Epilogue, p. 162 below. 44. Tupman would be paid £400 per year until July 1877 and £300 per year after that. Secretary of the Admiralty to G. B. Airy, 23 May 1876, RG0/6-267 no. 548. 45. G. Tupman to G. B. Airy, 2 March 1876, RGO/6-270 no. 335. 46. G. B. Airy to R. J. Ellersy, 10 January 1878, RGO/6-271 no. 288. 47. R. J. Ellersy to G. B. Airy, 20 March 1878, RGO/6-271 no. 289. 48. During the Queen’s visit to South Kensington on 13 May 1876. Airy, Autobiography, pp. 317–18.

192

Notes to pages 132–9

49. Secretary of the Admiralty to G. B. Airy, 9 May 1876, RGO/6-267 no. 475. 50. He cited 7,000 astronomical observations, of which over 5,000 had been fully reduced, not including the 600 or 700 photographs ‘to be examined’, of which very little else was said. W. H . M. Christie to Secretary of the Admiralty, 15 July 1876, RGO/6-269 no. 494. 51. Hansard’s Parliamentary Debates, 233 (19 April 1877). 52. G. B. Airy to G. Tupman, 30 April 1877, RGO/6-270 no. 389. 53. G. Tupman to S. J. Perry, 1 December 1876, RGO-6/270 no. 373–9. 54. The problems in Kerguelen seemed to confirm Tupman’s opinion, which he had held since the training phase, that Perry was unfit for the post of chief. ‘A more unpractical man I have never met’, he once told Airy. At one point, Tupman had proposed that Perry be demoted from station chief, but it was feared that not only would Perry quit, but Sidegreaves, another Jesuit, would go with him, ‘depriving the enterprise of the services of the Jesuits altogether’. Airy suggested a more subtle plan: ‘Try if you can manage it thus: leave Perry in the [supreme position] at Christmas Harbour, just as he understands it; and appoint (say Lieut. Corbet, an excellent man for the purpose) with some new title “Inspector of Antarctic Stations” (or something better) requiring him to assist Father Perry (and be so far subordinate to him) in setting him on his feet at Christmas Harbour’. G. Tupman to G. B. Airy, 24 December 1873, RGO/6-270 no. 152; G. Tupman to G. B. Airy, 8 January 1874, RGO/6-270 no. 155; G. B. Airy to G. Tupman, 9 January 1874, RGO/6-270 no. 157 (the reading of the bracketed words is unsure). 55. G. Tupman to G. B. Airy, 9 June 1877, RGO/6-270 no. 404. 56. G. B. Airy to G. Tupman, 30 April 1877, RGO/6-270 no. 389. 57. G. B. Airy to G. Tupman, 11 June 1877, RGO/6-277 no. 405–6. 58. Ibid. 59. G. Tupman to G. B. Airy, 6 June 1877, RGO/6-272 no. 415–16. 60. G. B. Airy to G. Tupman, 30 April 1877, RGO/6-270 no. 389 (emphasis in original). 61. G. B. Airy, Report on the Telescopic Observations of the Transit of Venus, 1874, Made in the Expedition of the British Government, and on the Conclusion Derived from Those Observations (London, 1877). Also reported and discussed in G. B. Airy, ‘On the Mean Solar Parallax from the Transit of 1874’, MNRAS, 38 (1877), p. 11. 62. G. B. Airy to Secretary of the Admiralty, 18 July 1877, RGO/6-267 no. 554–5 (emphasis in original). 63. Chapman, ‘Private Research and Public Duty’, p. 135. 64. Tupman, ‘On the Mean Solar Parallax’, p. 455. 65. E. J. Stone, ‘On the Telescopic Observations of the Transit of Venus 1874, Made in the Expedition of the British Government, and on the Conclusions to be Deduced from these Observations’, MNRAS, 38 (1878), p. 279; E. J. Stone, ‘A Comparison of the Observations of Contact of Venus with the Sun’s Limb in the Transit of 1874, December 8, made at the Royal Observatory, Cape of Good Hope, with the Corresponding Observations made at the Stations in the Parliamentary Report, and a Discussion of the Results’, MNRAS, 38 (1878), p. 341. 66. Tupman, ‘On the Mean Solar Parallax’, p. 455 (emphasis in original). 67. Ibid., p. 455. 68. Ibid., p. 455. 69. G. B. Airy to G. Tupman, 26 December 1878, RGO/6-272 no. 683–4. 70. G. B. Airy to Secretary of the Admiralty, 12 September 1877, RGO/6-267 no. 565. 71. G. L. Tupman to G. B. Airy, 8 January 1878, RGO/6-272 no. 687.

Notes to pages 139–44

193

72. W. Christie to G. B. Airy, 18 January 1878, RGO/6-271 no. 97. 73. G. B. Airy to W. Christie, 5 January 1878, RGO/6-271 no. 94 (the reading of the bracketed word is unsure). 74. G. B. Airy to W. Christie, 16 January 1878, RGO/6-271 no. 259. 75. W. Christie to G. B. Airy, 18 January 1878, RGO/6-271 no. 97. 76. W. Christie to G. B. Airy, 19/22 January 1878, RGO/6-271 no. 105. See also W. Christie to G. B. Airy, 18 January 1878, RGO/6-271 no. 97; and W. Christie to G. B. Airy, 18 January 1878, RGO/6-271 no. 97. 77. G. L. Tupman, ‘Ingress Photos’, undated, RGO/6-272 no. 721. 78. G. B. Airy to W. Christie, 21 January 1878, RGO/6-272 no. 102. 79. In Holly Rothermel’s discussion of the transit of Venus photography in ‘Images of the Sun’, she concludes that Airy blamed only the problem of discordance between measurers, and she thus argues that Airy blamed only the ‘personal equation’ and not the photographic method itself for the failure. However my research suggests that Airy placed the majority of the blame on the unresolved issue of scale, and on other aspects of photography itself. 80. G. L. Tupman, ‘On the Photographs of the Transit of Venus’, MNRAS, 38 (1878), p. 508, on p. 513. 81. G. B. Airy to Secretary of the Admiralty, 10 March 1878, RGO/6-267 no. 585–7. 82. Newcomb (ed.), Observations of the Transit of Venus, December 8–9, 1874. 83. Airy (ed.), Account of Observations of the Transit of Venus, p. 19. 84. Ibid., p. 56. 85. Hansard’s Parliamentary Debates, 248 (31 July 1879). 86. Ibid. 87. Hansard’s Parliamentary Debates, 253 (28 June 1880). 88. Hansard’s Parliamentary Debates, 309 (16 September 1886), Civil Service Supply Estimates. 89. Hansard’s Parliamentary Debates, 248 (31 July 1879). 90. Airy, Autobiography, p. 347. 91. Struve wrote to Simon Newcomb soon after Airy’s retirement: ‘Whether and how far Christie will grow in the task must be taught by experience … But just because he is still an unknown quantity, the hope of a solid and skillful performance remains not excluded, while the other competitors of whom there was talk (Stone, Proctor, Lockyer) from here indeed seem to be very questionable. It will please you, I think, to hear that with the first report of this retirement, here in Pulkovo, quite independently on many sides was expressed “What a pity Newcomb is no Englishman.”’ A. H. Batten, Resolute and Undertaking Characters: The Lives of Wilhelm and Otto Struve (Dordecht: Reidel, 1988), p. 191. 92. Daily News (London), 19 January 1875. 93. J. L. L. Crawford, ‘General Lindsay-Copeland’, Dun Echt Correspondence, ROE, A 30.193. 94. Harkness, ‘Address by William Harkness’, pp. 87–8. 95. Tupman, ‘On the Photographs of the Transit of Venus’, p. 508. 96. Newcomb (ed.), Observations of the Transit of Venus, December 8–9, 1874. 97. S. Newcomb, Reminiscences of an Astronomer (London: Harper, 1903). 98. Dick et al., ‘Simon Newcomb, William Harkness’; Dick, Sky with Ocean Joined. 99. W. Harkness, The Solar Parallax and its Related Constants (Washington, DC: Government Printing Office, 1891).

194

Notes to pages 144–9

100. A preliminary report had also been published in 1877: B. Hasselberg, Russische Expeditionen Zur Beobachtung Des Venusdurchgangs 1874 (St Petersburg: n.p., 1877); T. Wittram, Zusammenstellung Der Contactbeobachtungen Und Ableitung Der Geographischen Coordinaten Der Beobactungstationen (St Petersburg: Kaiserlichen Akademie der Wissenschaften, 1891). On the results of the Russian expeditions, see Werrett, ‘Transits and Transitions’; and Batten, Resolute and Undertaking Characters. 101. A. Auwers, Die Venus-Durchgänge 1874 Und 1882: Bericht Über Die Deutschen Beobachtungen Im Auftrage Der Commission Für Die Beobachtung Des Venus-Durchgangs, 3 vols (Berlin: Commission fuer die Beobachtung des Venus-Durchgangs, 1895). 102. Comptes Rendus, 100 (1885), pp. 227–30, 341–93, 1121, cited in Dick, Sky with Ocean Joined; V. -A. Puiseux, Recueil de Mémoires, Rapports et Documents Relatifs à l’observation du Passage de Vénus sur le Soleil, 3 vols (Paris: Mémoires de l’académie des Sciences de l’institut de France, 1877–90). 103. Dick et al., ‘Simon Newcomb, William Harkness’; Staley, ‘Conspiracies of Proof and Diversity of Judgement’. 104. W. Harkness, ‘On the Value of the Solar Parallax Deducible from the American Photographs of the Last Transit of Venus’, Astronomical Journal, 8 (1888), p. 108. 105. Harkness, The Solar Parallax, pp. 51–4. 106. Werrett, ‘Transits and Transitions’. 107. Anon., ‘The German Heliometer Observations of the Transits of Venus, 1874 and 1882’, MNRAS, 55 (1895), p. 243. 108. Anon., ‘Solar Parallax from Transit of Venus Observations’, MNRAS, 61 (1901), p. 267. 109. S. Newcomb, The Elements of the Four Inner Planets and the Fundamental Constants of Astronomy (Washington, DC: Government Printing Office, 1895), pp. 155–8. 110. Dick, Sky with Ocean Joined, p. 321.

Conclusion 1.

2. 3. 4.

5. 6. 7. 8.

9.

S. de Chadarevian, ‘Graphical Method and Discipline: Self-Recording Instruments in Nineteenth-Century Physiology’, Studies in the History and Philosophy of Science, 24 (1993), pp. 267–91, on pp. 278–9. T. S. Kuhn, ‘The Function of Measurement in the Physical Sciences’, Isis, 52:2 (1961), pp. 161–93. J. O’Connell, ‘Metrology: The Creation of Universality by the Circulation of Particulars’, Social Studies of Science, 23:1 (1993), pp. 129–73. L. Derksen, ‘Towards a Sociology of Measurement: The Meaning of Measurement Error in the Case of DNA Profiling’, Social Studies of Science, 30:6 (2000), pp. 803–45, on p. 829. H. Chang, Inventing Temperature: Measurement and Scientific Progress (Oxford: Oxford University Press, 2004). G. Gooday, The Morals of Measurement: Accuracy, Irony, and Trust in Late Victorian Electrical Practice (Cambridge: Cambridge University Press, 2004). Kuhn, ‘The Function of Measurement in the Physical Sciences’. See K. M. Darling, ‘The Complete Duhemian Underdetermination Argument: Scientific Language and Practice’, Studies in History and Philosophy of Science, 33 (2002), pp. 511–33. D. Gill to G. B. Airy, 28 October 1880, RGO/6-283 no. 215–16.

Notes to pages 149–57

195

10. Lord Kelvin, W. Thompson, ‘Electrical Units of Measurement (1883)’, in Kelvin, Popular Lectures and Addresses, 3 vols (London: Macmillan and Co., 1889–94), vol. 1, pp. 73–136, on pp. 73–4.

Epilogue 1. 2. 3. 4. 5.

6.

7. 8.

9. 10.

11.

12. 13.

14. 15. 16. 17.

D. Gill to G. B. Airy, 28 October 1880, RGO/6-283 no. 215–16. Airy, ‘On the Preparations to be made for Observation’, p. 381. Anon., ‘The Transit’, The New York Times, 7 December 1882. G. B. Airy to Capt. Evans, 10 April 1880, RGO/6-283 no. 4 (emphasis in original). A letter from Struve to Spottiswoode was reprinted in The Times (London), 8 December 1882, in which Struve explained, ‘Experience since 1874 has sufficiently proved that there is no prospect whatever, even with combined international efforts, of obtaining by the present transit a geometrical determination of the parallax of the sun, which would not be soon surpassed in accuracy by other recent methods (for example, that suggested by Mr. Gill), methods which are capable of being repeatedly employed and that without any costly expeditions’. Within a few months Airy rescinded the nomination, but it did not stop Stone from being elected Directing Astronomer in early 1881. G. B. Airy to Secretary of the Admiralty, 18 September 1880, RGO/6-283 no. 9. Ibid. Transit Committee of the Royal Society, Report of the Committee of the Royal Society Appointed for the Purpose of Advising the Treasury and the Admiralty with Respect to the Conduct of the Transit of Venus Observations in 1882 (London: Royal Society, 1880). Secretary of the Admiralty to G. B. Airy, 13 December 1880, RGO/6-283 no. 11–14. G. B. Airy to Secretary of the Admiralty, 18 September 1880, RGO/6-283 no. 9 (emphasis in original). Another example of Airy’s attitude towards committees comes from a reply to Hind’s invitation to Airy to join the preliminary committee, to which he replied ‘I shall be most happy to act as I can with the proposed committee. But you know the difficulty that I have in a committee-[situation] and I think that my service would be best rendered in writing.’ G. B. Airy to J. R. Hind, 1 December 1880, RGO/6-283 no. 39–40 (the reading of the bracketed word is unsure). A reason later given was related to ‘the small control which the Admiralty can exercise over the expenditure’. ‘Minutes of the Board of the Admiralty’ (1881), PRO ADM 167/13. Transit Committee of the Royal Society, ‘Minutes of the Meetings of the Transit Committee of the Royal Society of London’ (1881–4), RGO-6/283 no. 141–91. For example, a request to send British delegates to the International Commission meeting in Paris was denied, a request for seven or eight engineers to be temporarily transferred to the transit project was rejected (because ‘there will be an exceptional pressure for trained soldiers of the Royal Engineers next year’), and a request to build the observation huts at the government dockyards was similarly brushed off. ‘Minutes of the Board of the Admiralty’ (1881), PRO ADM 167/13; RGO-6/283 no. 172. To keep the price of these new instruments down, the photoheliographs were dismantled and the mountings transferred to the new telescopes. Anon., ‘The Transit of Venus’, The Times (London), 22 February 1881, p. 10. Anon., ‘The Coming Transit of Venus’, The Echo (London), 1 March 1881. Quoted in Hutchins, ‘British University Observatories C1820–1939’, p. 126.

196

Notes to pages 157–64

18. R. Hutchins, ‘British University Observatories C1820–1939’, p. 126. In contrast to the Radcliffe, the new Oxford University Observatory, De La Rue’s benefactee, was among the richest. Ibid., p. 113. 19. G. G. Stokes to G. B. Airy, 24 January 1881, RGO/6-283 no. 44–6. 20. G. B. Airy to G. G. Stokes, 31 March 1881, RGO/6-283 no. 47. 21. G. B. Airy to G. G. Stokes, 11 February 1881, RGO/6-283 no. 52. 22. Airy also seems to have forgotten that in Tupman’s final analysis of the 1874 data he did include the German observations at Thebes. 23. C. Cornu to Spottiswoode, 26 January 1881, RGO/6-283 no. 49. 24. W. H. M. Christie, ‘The Transit of Venus in 1882’, MNRAS, 42 (1882), p. 181. 25. Transit Committee of the Royal Society, ‘Minutes of the Meetings of the Transit Committee of the Royal Society of London’ (1881–4) RGO/6-283 no. 169. 26. Quoted in Christie, ‘The Transit of Venus in 1882’. 27. E. J. Stone, Transit of Venus, 1882: Report of the Committee Appointed by the British Government to Superintend the Arrangements to be made for the Sending of Expeditions at the Government Expense, and Securing Co-Operation with the Government Expeditions for the Observation of the Transit of Venus, 1882 December 6 (London: Committee on the Transit of Venus 1882, 1889), p. 2. 28. G. B. Airy to G. G. Stokes, 11 February 1881, RGO/6-283 no. 52. 29. G. B. Airy to Spottiswoode, 2 March 1882, RGO/6-283 no. 54. 30. D. Gill to G. B. Airy, 28 October 1880, RGO/6-283 no. 215–16. 31. J. L.L. Crawford, ‘General Lindsay-Copeland’, Dun Echt Correspondence, ROE, A 30.193. 32. G. B. Airy to Spottiswoode, 2 March 1882, RGO/6-283 no. 54. 33. Transit Committee of the Royal Society, Report of the Committee, p. 315. 34. An article in the Observatory compared the three versions of instructions: Anon., ‘The Instructions for Observing the Transit of Venus, 1882’, Observatory, 5 (1882), pp. 315– 19. 35. Anon., ‘The Transit of Venus’, The Times (London), 2 December 1882, p. 4. 36. S. Newcomb, ‘Remarks on the Instructions for Observing the Transit of Venus Formulated by the Paris International Conference’, MNRAS, 42 (1882), p. 275, on p. 275. 37. Stone, Transit of Venus, 1882, p. 2. 38. E. N. Swainson to the Chair of Board of Visitors to Greenwich, 13 June 1882, PRO ADM 190/14. 39. G. B. Airy, ‘The Annual Visitation at Greenwich’, Astronomical Register, 19:2 (1881), pp. 165–74. See also ‘Visitors of the Royal Observatory at Greenwich Minute Book’, PRO ADM 190/4. 40. E. N. Swainson to the Chair of Board of Visitors to Greenwich, 13 June 1882, PRO ADM 190/14. 41. Ibid. 42. O. W. Holmes, The Complete Poetical Works of Oliver Wendell Holmes (London: Sampson Low & Company, 1895), pp. 248–86. 43. Stone, Transit of Venus, 1882, p. 2. 44. Apparently Tupman’s low opinion of Perry – that he was not fit to be a station chief and that the Kerguelen station had been mismanaged – was not taken into consideration by the committee. In the report for 1882, Perry’s observations caused some confusion and were sometimes left out of the calculations by Stone. See Stone, Transit of Venus, 1882, p. 77.

Notes to pages 165–71 45. 46. 47. 48.

49. 50. 51. 52. 53. 54. 55. 56. 57. 58.

59. 60.

61. 62.

63.

64.

65.

197

Hardy, Two on a Tower, pp. 234, 245. W. H. M. Christie, ‘The Transit of Venus’, The Times (London), 6 December 1882, p. 8. Anon., ‘The Transit of Venus’, The Times (London), 7 December 1882, p. 5. A summary of expedition events is also in: E. J. Stone, Report of the Radcliffe Observer to the Board of Trustees, Appendix to the Radcliffe Observations, 1881 (London: Committee on the Transit of Venus, 1882), p. 7. Anon., ‘Across the Sun’s Face’, The New York Times, 7 December 1882. Stone, Transit of Venus, 1882, pp. 4–7. Ibid., p. 5. Ibid., p. 8. The success of the budget management cannot be verified, however, as no final statement of the costs for 1882 has been found. Quoted in Lankford, ‘The Impact of Photography on Astronomy’, p. 29. Ibid., p. 23. Ibid., p. 29. Quoted in ibid., p. 36. Ibid., p. 32. Hutchins, however, argues that the rapid growth of astrophysics in the United States was due to the ‘decentralized’ structure of the profession, which allowed the most talented individuals to succeed, and to the endowment of research by private donors. In contrast, the hierarchical structure of the profession in France, Germany and Russia, did not make the best use of talent, and Britain, though also decentralized, was lacking in major benefactors. R. Hutchins, ‘British University Observatories C1820–1939’, p. 230. P. Laurie, ‘Greenwich Observatory’, in Gingerich (ed.), Astrophysics and Twentieth-Century Astronomy, pp. 198–207. W. H. M. Christie, Photo-Heliographical Results 1874 to 1885 Being Supplementary Results from Photographs of the Sun Taken at Greenwich and Harvard College, U.S.A., at Melbourne, in India, and in Mauritius in the Years 1874 to 1885 and Measured and Reduced at the Royal Observatory, Greenwich (Edinburgh: Neill Co., 1907). Quoted in Lankford, ‘The Impact of Photography on Astronomy’, p. 33. S. Newcomb, ‘Feasability of Determining Solar Parallax by Observations of the Planet Eros During Opposition, 1900–01’, Astronomical Journal, 20:480 (1900), pp. 189–91, on p. 189. L. Pigatto and V. Zanini, ‘Eros Opposition of 1900 and Solar Parallax Measurement’, paper given at the Meeting of the Astronomische Gessellschaft at the Joint European and National Astronomy Meeting of the European Astronomical Society (Munich, January 2001). W. H. M. Christie, Observations of the Planet Eros 1900–1901 for Determination of the Solar Parallax from Photographs Taken and Measured at the Royal Observatory Greenwich (London: Royal Greenwich Observatory, 1908). R. V. D. R. Woolley, ‘Harold Spencer Jones. 1890–1960’, Biographical Memoirs of Fellows of the Royal Society, 7 (November 1961), pp. 136–45, on p. 139; H. S. Jones, ‘The Solar Parallax and the Mass of the Moon from Observations of Eros at the Opposition of 1931’, Memoirs of the Royal Astronomical Society, 5th series 66:2 (1941).

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INDEX

Abney, William de Wivelslie 72–3, 76, 96–7, 117, 121, 126–7, 169, 184, 187, 191, 199 collodio-albumen process 72–3 Abyssinia 72 Adams, John Couch 51, 156 Adelis, Miss 98, 111 Aden 100, 105 Admiralty 2, 5, 6, 21–4, 26–7, 41–4, 49–52, 63–4, 82, 130–3, 135–6, 141–3, 155–7, 163–4, 183, 191–3, 195 Hydrographer’s Office 43, 142 Manual of Scientific Enquiry 26, 28, 177, 205 Admiral Mouchez 158 relationship to amateur science 28, 32, 72 Admiral Sands 183, 190 science funding 25–7 Airy, George Biddell 29, 31–3, 35–6, 46–54, 58–9, 63–5, 72–87, 101–3, 106–8, 121–3, 125–36, 138–41, 143, 154–8, 160–3, 177–9 beam-compass micrometer 128, 139 in the historiography 32–5 and international cooperation 87, 195 management of Greenwich 31, 58–9, 83, 85, 101, 167–8 management of programme 8, 57–9, 83, 121, 167–8 and Proctor, debate 48–56, 65, 79, 119, 126, 135 and Scoresby, controversy 178, 203 Alexandria 95, 106 Algiers 24 Allahabad see India altazimuth 83, 97, 99, 100, 111, 156 Alvin Clark & Sons see instrument makers

amateur science culture 7, 13, 25, 27–8, 31, 46, 76–8, 94, 147, 165 relationship to Admiralty science 28, 32, 72 relationship to Greenwich 7, 33, 57–8, 60, 74, 76–8 relationship to state funding debate 15, 41 André, Charles 85, 185 Angola 14 Antarctic exploration 22–3, 49–53, 103, 164 Arago, François 23, 28 Arctic expeditions 22, 163 Argentine Republic 159 Ascension Island 143 astronomical instruments 82, 102, 131, 156 astronomical photography objectivity and 59–60 precision measurement and 61–73, 168 transit of Venus method see photographic method atmosphere and observation 70, 82, 140, 162 of sun 41, 67, of Venus 79, 82, 111, 128 Australia 3, 84, 91, 103, 110, 136, 160, 163–4 Brisbane 164 Melbourne 110, 132 New South Wales 1, 164 Queensland 164 South Australia 164 Sydney 1, 110, 132, 138, 163 Sydney Observatory 129 Auwers, Arthur 45, 57, 75, 78, 87

– 213 –

214

The Transit of Venus

Babbage, Charles 25–30, 44, 112 Bailey’s Beads 61 Banks, Joseph 9 Barbados 164 Barrow, John 22 Baxendall, Joseph 40 Belmont see Mauritius Bencoolen 14–15 Berlin see Germany Bermuda 163–4 Bessel, Karl Friedrich Wilhelm 84 Bethel, Commander 142 Bey, Ismail 101, 108, 113 Bey, Mahmoud 108, 113, 136 big science 6, 21–5, 28, 33, 150–1 Biot, Jean-Baptiste 23 black drop effect 17–18, 37–40, 57, 75, 79–81, 111–13, 128–30, 160–2 cusps 84, 109, 162 phases 83–4, 111, 128–9, 132–6, 159– 61, 166–7 Board of Visitors to Greenwich see Greenwich Bombay see India Bond, Henry 60–3 Bradley, James 13–14, 50 Brazil 159 Breslau see Poland Brewster, David 25 Brisbane see Australia British Association for the Advancement of Science (BAAS) 22, 25, 28–9 British Consul-General in Egypt 95 British East India Company see East India Company British Empire 28, 33, 90, 92, 99 Browne, C. Orde 79, 94–6, 98, 100–1, 107–8, 111–13, 136 Bull, John 107 Burton, Charles 117, 128, 130, 132, 138–9 Cadiz see Spain Cairo see Egypt Calcutta see India Cambridge University 25, 47, 51, 80, 156 Campbell, Mrs 117, 136 Canada 164 Toronto 24

Cape of Good Hope 13, 15, 24, 160, 163–4 Cape Town 103 Carpenter, H. J. 166 Carte du Ciel 168–71 Challenger expedition 6, 33, 52, 131, 142 Chappe, Jean-Baptiste 39 Chary, C. Ragoonatha 92–4 Chatham Naval School 72–3 Chicago see United States Childers, Hugh 43, 133, 142 Chile 159 China 106, 154 Peking 24 Shanghai 115 Christchurch see New Zealand Christie, William H. M. 58, 73, 85, 126–7, 132–3, 135–6, 139–40, 143, 165, 169–71 chromatic aberration 69, 70 chronometer 30, 83, 102–5, 108, 111–12, 158, 163 Clerk Maxwell, James 1, 4, 21, 150, 173, 202 Clerke, Agnes 1, 37 collodio-albumen process see Abney, William de Wivelslie colonial science 14, 17, 22–4, 29, 32, 89, 90–2, 97, 114, 132, 150, 163–4 Columbia College Observatory see United States Conferénce Internationale des Etoiles Fondamentales 145, 168 Cook, Captain James 3, 5, 17, 9, 44, 80, 92, 94, 137 Cornu, Alfred 88, 158 Cornwall 106 Crawford, Earl of see Lindsay, James Ludovic daguerreotype 74, 76 Dallmeyer see instrument makers Darwin, Charles 21, 112, 150, 164 Darwin, Leonard 117, 164 De La Rue, Warren 7, 52, 60–5, 67–70, 73– 7, 121, 125–6, 139–40, 156, 170–1 De La Rue scale 69, 70, 127 De La Rue & Company 60 Delisle, Joseph-Nicolas 13, 47 Denmark 17, 159 Dent see instrument makers

Index Devonshire Commission 41, 42, 45, 52 Dixon, Jeramiah 15 Dolland, John see instrument makers Dublin 24, 41, 114–15 Duhem, Pierre 149 Dun Echt Observatory 46, 74 East India Company 9, 14, 23–4 Eastern Extension Australasia and China Telegraph Company 163 Eastern Telegraph Company 106 Education, Board of 28 Edward James Stone 37, 129, 155–6 Egypt 42, 88, 91, 94, 99, 100, 105–6, 111, 125 Cairo 7, 24, 90, 94–6, 98–101, 103, 105–7, 111, 113, 121–2, 187 Cairo Observatory 98–9, 108, 113, 136 Khedive Isma’il see Isma’il, Khedive of Egypt Luxor 108, 136 Mokattam Hills 95–6, 107–8, 111–12 Suez 105–6, 108 Encke, Johann Franz 35 Eros 170–1 errors 62–3, 122, 124–5, 135, 149, 159 of instruments 86–7, 101–2, 104–5, 125, 139, 149 least squares 123–5 of personality see personal equation probable error 61, 74, 125, 127, 129, 135, 137 Europe 7, 13, 45, 89, 90, 93, 99 failures 8, 18, 25, 50, 119, 138, 140–1, 143, 149, 154, 156, 167 Faraday, Michael 150 Faye, Hervé 76 Forbes, George 74, 80–1, 84, 100, 108, 16 Foreign Office 158–9 France 2, 5, 13–15, 17, 23, 25, 45, 57, 70, 74–6, 85, 88, 99, 144–5, 158–9, 166 Paris 45, 145, 158–9, 175 Paris International Exhibition 41 Paris Observatory 23, 36, 158 Franco-Prussian War 45 Franklin, Benjamin 175

215

Fraunhofer see instrument makers funding of eighteenth-century programmes 14 of nineteenth-century programmes 43, 45, 121, 131–2, 140, 170 Geological Survey of Great Britain 33 geometric contact 38, 80, 84 Germany 2, 5, 17, 23–5, 45, 51, 57, 70, 74–5, 77, 85, 90, 144–5, 158–9, 166 Berlin 57, 105 Berlin Academy 45 Berlin Observatory 45 Munich 24 Gibraltar 106 Gill, David 71, 74, 84, 104–5, 108, 136, 143, 149, 153, 160–1, 166 Gold Coast 14 Graham, George see instrument makers gravitational theory method 30, 36, 144 Great Exhibition 2, 60 Great Trigonometrical Survey of India 33 Green, Charles 17 Greenwich, Royal Observatory 6–8, 29–33, 57–9, 65, 75–8, 82–7, 101–5, 107–8, 125–7, 155–7, 163, 170–1, 178, 196–7, 202–4 cultural status of 30–2, 35, 148 historiography of 32–5 Board of Visitors to 51–2, 63, 163 relationship to Admiralty 30, 102, 162–4 Grubb see instrument makers Haiti 17 Hall, Asaph 73 Halley, Edmond 9–11, 13–5, 17, 37, 47, 51, 53 Hansen, Peter A. 26, 36 Harkness, William 12, 143–5 Hartnup, John 40, 104 Harvard College Observatory see United States Hawaii 42, 92, 100, 103, 108, 110, 125, 128 Honolulu 79, 108–10, 121 heliometric method 74–6, 86–7, 143, 145, 177 Herschel, John 21–3, 26, 31–2

216

The Transit of Venus

history, role of 3, 11–3, 15, 21, 23, 91–3, 165 Hind, J. R. 155–7 HMS Challenger see Challenger expedition HMS Endeavour 17 Honolulu see Hawaii Horrox, Jeramiah 11, 15 Hudson’s Bay 17 Huggins, William 156 Humboldt, Alexander von 4, 23 Huxley, Thomas 112, 155 Hydrographer’s Office see Admiralty Illustrated London News 96–7 Imperial Observatory of Russia see Russia impersonality 3, 59, 86, 100, 134 India 65, 84, 93, 106, 110 Allahabad 114, 187, 189, 201 Bombay 24, 105 Calcutta 94, 111 Calcutta Observatory 36 Karachi 111 Lahore 111 Lucknow 24 Madras 24, 93, 111, 136 Madras Observatory 65, 92, 94 Pondicherry 14–15, 17 Roorkee 110 Trivandrum 24 Indian astronomy 53, 92–4, 111 Inland Revenue, Board of 60 instrument makers Alvin Clark & Sons 76 Dallmeyer 63–4, 67, 70 Dent 98, 108 Dolland, John 14 Fraunhofer 74 Graham, George 17 Grubb 156 Martin, Benjamin 10, 77 Repsold, A. & G. 74 Short, James 16 Stackpole 76 Steinheil 70 instrumental error 86, 101, 124–5, 139 internal contacts 39, 81, 108–10, 128–9, 141, 161, 166 International Astronomical Union 168

international exhibitions 41–2, 54–5 International Geodetic Association 168 internationalism in science 2–5, 18–19, 34–5, 86–7, 123, 145, 158–9, 168–9 irradiation 81–2, 126–8 photographic 70–2, 126–8, 138–40 Isma’il, Khedive of Egypt 95, 98–100, 108, 113 Italy 45–6, 92, 158 Jamaica 164 Janssen, Pierre Cesar Jules 75 photographic revolver 60, 76, 87, 110, 125, 131, 141 Japan 136 Nagasaki 114 Jesuit astronomy 16, 175 Father Perry see Perry, Stephen J. Father Sidgreaves see Sidgreaves, Walter Karachi see India Kerguelen Island 42, 51, 91, 100, 103, 108, 111, 113, 133, 135, 158 Kew Observatory 29, 62–3, 68, 126, 170 Lahore see India Lalande, J. J. F. 18, 82 Lassell, William 40 latitudes 7, 47, 60, 99, 100, 102, 115, 127–8 Le Gentil, Guillaume 15, 17 Le Verrier, Urbain 36, 88, 144 Library Company of Philadelphia 17 Lindsay, James Ludovic, Earl of Crawford, 46, 71–2, 74–6, 84, 86, 104–5, 111, 119, 126, 143, 156 Lisbon see Portugal Lithuania University Observatory, Vilnius 67 Liverpool Observatory 30, 40, 104–5 local time 11, 47, 99, 100, 102–3, 105, 107 Lockyer, J. Norman 29, 41, 52, 57, 67, 77, 80 longitude 30, 35, 102, 115, 127, 163–4, 168 chronometric 101–5, 143 lunar distance method 102–3, 162 of stations 16, 46–7, 50, 124, 132–3, 144, 162–4 submarine telegraphic 86, 102, 105–8, 162–4

Index

217

Lowey, Benjamin 29, 62 Lucknow see India Luxor see Egypt Lyttleton see New Zealand

Newton, Emily 98, 111–12, 136, 159 Newton, Lieutenant 99–101, 108, 111–12 Noble, Lieutenant 109 Norway 17, 23

Madagascar 14, 105, 163–4 Madras see India Magnetic Crusades 6, 22, 24–5, 27–9, 33, 150–1 Malta 40, 106–7 maps 13–14, 47–8, 50, 52 Martin, Benjamin see instrument makers Mars, opposition of 13, 36, 38, 143–4, 153 Maskelyne, Nevil 14, 32 Mason, Charles 15 Mauritius 46, 71, 84, 105, 111, 164 Belmont 105 Melbourne see Australia members of parliament 26, 44, 51, 54, 133, 141–2 Mercury, transit of 6, 9, 10, 13, 37, 40–1, 86 Michelson, Albert 144 modelling 7, 77–88, 167, 170 experiments with 80–2 results of 109–13, 125, 128–30, 141 submarine cable 106 training observers with 82–5, 159–60, 170 Mokattam Hills see Egypt Munich see Germany

objectivity 59 and impersonality see impersonality observation language 16–17, 38–9, 84–6, 130, 133–6, 147, 149, 161, 166 observation stations 35, 42, 46, 48, 56, 65, 94, 100, 102, 132 observatories Berlin see Germany Cairo see Egypt Calcutta see India Columbia College see United States Dun Echt see Dun Echt Harvard College see United States Imperial, of Russia see Russia Kew see Kew Lithuania University, Vilnius see Lithuania Liverpool see Liverpool Madras see India Oxford University see Oxford Paris see France Pulkovo see Poland Radcliffe, Oxford see Radcliffe Royal Greenwich see Greenwich Sydney see Australia United States Naval, Washington see United States observer judgements 84, 159 reports 39, 121, 128, 130, 140, 166–7 Otago Philosophical Institute see New Zealand Oxford University 25, 74, 155, 157, 168–9 Observatory 126, 170

Nagasaki see Japan Natal 164 nationalism 2–3, 55–6, 116 in science 2–5, 14–15, 23–5, 41–2, 45–6, 49–52, 74–6, 87, 116, 150–2, 158 Nautical Almanac 48, 102, 115, 123, 157 Neptune, discovery of 35, 50 Netherlands 17, 46, 159 Brussels 24 Newcomb, Simon 31, 39, 40, 66, 69, 74, 76, 86, 144, 162, 169–70 newspapers see popular press New South Wales see Australia New York City see United States New Zealand 92, 110, 113, 132, 163–4 Christchurch 51 Lyttleton 92 Otago Philosophical Institute 92

parallax see solar parallax Paris see France parliament 1, 26, 29, 41, 43–4, 51, 63, 133, 135, 141–2 Pascha, Hassein 100 Peking see China Perry, Stephen J. 103, 111, 133 Persia 90

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personal equation 1, 2, 31, 84–6, 100–1, 138–9 Peru 154 Petrie, Flinders 88 photographers 61, 64–5, 72, 75 photographic measurements 61–2, 124, 171 photographic method chemistry of 70–4, 127, 148, 169 long vs short focus optics debate 68–71, 75–6, 119, 126–7, 140, 143–4, 169 photographic revolver see Janssen, Pierre Cesar Jules photoheliograph 63–5, 67, 83, 97, 126–7, 132–3, 138, 141 physical sciences 4, 147, 170 Piazzi Smyth, Charles 88, 91 Pogson, Miss 136 Pogson, Norman 36, 94 Poland Breslau 24 Pulkovo Observatory 45, 78, 87, 100, 154, 165 Polynesia 91 Pond, John 32 Pondicherry see India popular press 2–5, 7, 13–14, 29, 43, 46, 49–56, 72, 76, 90–1, 97, 110, 114– 18, 119, 132, 154, 165 Daily News (London) 96, 114 Echo (London) 114, 153, 157 Edinburgh Review 35, 48, 53–4 Farmer’s Almanac 4 Graphic (London) 4, 78 Hawaiian Gazette 110 Illustrated London News 97 Irish Times x, 9, 41, 56, 114 Nature 11, 65, 119 New York Times 34, 45–6, 53, 153, 165 New Zealand Herald 114 North China Daily News 114 Otago Guardian 92 Punch 55–6, 91, 147 Scribner’s Monthly 56 Spectator 49–50 Sydney Morning Herald 1–3, 151 The Times (London) 49–50, 51, 113, 115–16, 119 science journalism 54

Porthcurno telegraph station 106–7 Portugal 9, 14, 16, 159 Lisbon 106 positional astronomy 6, 29, 30, 33 probable error see errors Prague 24 precision measurement 4, 30–2, 148–9 in astronomical photography see astronomical photography cultural value of 4, 30–3, 48–9, 93, 116 of longitude 101–7 management of errors in 124–6, 135, 149 practices of 83–4, 100–7, 125–6 of transit of Venus 4–5, 10, 16–17, 33, 87 Pritchard, Charles 170 Proctor, Richard Anthony 25–6, 47–54, 56, 65, 79, 119, 126, 129, 135, 143 and Airy see Airy, George Biddell Queensland see Australia Radcliffe Observatory, Oxford 74, 155, 157, 160, 168 reform movement 25–7, 41 Renan, Ernest 3, 116 Repsold, A. & G. see instrument makers Reunión 46 Reuters News Service 113–14, 119 Rodriguez 14, 51, 97, 100, 111, 134–5 Roorkee see India Royal Artillery 22, 24, 27, 164 Royal Astronomical Society 36, 39, 48, 52, 58, 61, 126, 155, 157 Royal Engineers 26–7, 72, 74, 126–7, 156, 164 College of Royal Engineers 156 Royal Greenwich Observatory see Greenwich, Royal Observatory Royal Marine Artillery 7, 27, 58, 78, 164 Royal Naval College 26, 58 School of Photography 72 Royal Society 14–15, 17, 42, 61, 77, 155–7, 162, 164, 168 Russell, Henry 129 Russia 2, 5, 15–17, 23–4, 43, 45, 51, 53, 70, 74–5, 77, 79, 86, 100, 144, 158, 166 Imperial Observatory of Russia 78

Index Russian Academy 14 St Petersburg 13–14, 45 Siberia 14, 50, 144 Rutherfurd, Lewis M. 67, 125, 190 Sabine, Henry 22–4, 27–8, 30 Saint-Domingue 17 St Helena 9, 14, 24, 37 St Petersburg see Russia Schwarzschild, K. 169 science culture 5, 21, 25–7, 30–1, 94, 150 education 25–6, 28, 41 and the state see state science workers 26–7, 54, 131 scientific progress 3–5, 11–12, 18–19, 24–5, 41, 55, 115–16, 148, 150–1 Shanghai see China Short, James see instrument makers Siberia see Russia Sidgreaves, Walter 164 Simla 24 Singapore 1, 24, 163–4 solar eclipse 61–3, 73 solar parallax 10–11, 13, 18, 35, 39, 47–8, 60, 66, 69, 84, 91, 93, 123–5, 134–6, 141, 144–5, 153, 170–1 Southern Ocean 17, 51–2 South Australia see Australia South Indian Ocean 103 South Kensington Museum 25, 132 Special Loan Collection 156–7 Spain 17, 159 Cadiz 24 Vigo 106 speed of light method 36, 38, 148 Spottiswoode, William 155, 158, 162 Stackpole see instrument makers Stanton, General 95, 99 state science 22, 23, 25–7, 29, 42–3, 131, 150, 156, 170 Steinheil see instrument makers Stewart, Balfour 62 Stokes, George 156 Stone, Edward James 38–40, 80, 129–30, 136–7, 140, 154, 156–7, 165–7 management of 1882 programme 154–7, 167–8

219

Strahan, Captain 110 Strange, Alexander 41, 52 Struve, Otto Vasilevich 45, 75, 87, 143 Sub-Marine Telegraph Service 142 submarine telegraphy see longitude Suez see Egypt Suez Canal Company 98–9 sunspots 62, 68, 80, 170 Sweden 17, 46 Sydney see Australia Sydney Morning Herald 1, 2, 151 Tahiti 3, 17 Tasmania 24 Tennant, J. F. 94, 110–11 Thompson, J. J. 107 Thompson, William 25, 150 Toronto see Canada Trade, Board of 28 transatlantic cable 106 transit circle 29, 125 clock 97, 100–1, 108 instrument x, 83, 97 transit of Mercury 6, 10, 13, 37, 40–1, 86 Treasury 14, 28, 41, 130–1, 138, 140, 142, 156, 159, 191, 195, 210 Trivandrum see India Tupman 42, 58, 75, 82, 84, 101, 109–10, 117, 121, 128–41, 144, 160–2, 167, 169 Tyndall, John 28 United States 2, 5, 7, 12–13, 45–6, 53, 57, 70, 72, 74–6, 90, 106, 115, 145, 154, 158–9, 163, 166, 170, 181, 209 Chicago 128, 165 Columbia College Observatory 67 Commission for the Transit of Venus 39–40, 67, 140 Harvard College Observatory 60–1, 69 Naval Observatory, Washington 39, 45, 73, 79, 106 New York City 47, 165 Secretary of the Navy 141 Varley, Cromwell 106 Verne, Jules 90

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Victoria, Queen 44, 51, 132 Victorian science see science Vienna 14, 70, 165, 169 Vigo see Spain War Office 23, 27 Washington, Naval Observatory see United States Whitehall 63 Whewell, William 22 Winlock, Joseph 69, 76 Wolf, Charles 85 Woolwich Arsenal 22, 24