1 THE EARLY DEVELOPMENT OF SPECTROSCOPY AND ASTROPHYSICS Thesis presented for the Degree of Doctor of Philosophy in the field of History of Science by Frank Arthur John Lord James Department of History of Science and Technology Imperial College of Science and Technology University of London March 1981 ABSTRACT 2 The Early Development of Spectroscopy and Astrophysics Frank Arthur John Lord James In 1800 there was no real interest in studying either the spectrum or the constitution of the stars. By 1870 spectro- scopy and astrophysics were among the most intensely pursued subjects in the physical sciences. The purpose of this thesis, therefore, is to examine how this change came about. I shall argue that the development of the undulatory theory of light and of the first two laws of thermodynamics identified the existence of problems in spectroscopy and astrophysics, and therefore brought these sciences into being. The success in the first half of the nineteenth century of the undulatory theory of light in accounting accurately for a large number of optical phenomena led naturally to the study of those phenomena which were not immediately reconcilable with the theory: absorption, emission, fluorescence, etc. These phenomena could be studied experimentally only by an examin- ation of the behaviour of their spectra, Therefore, in order to reconcile these phenomena with the undulatory theory, it was necessary to devise hypotheses which described the manner in which ponderable matter interacted with the luminiferous aether, There were two consequences of this work that were not directly related to solving the problems of the undulatory theory. It was realised that spectra could be used for the purpose of chemical analysis. And it was discovered that interpretations of the solar spectrum provided information concerning the physical constitution of the sun, Thermodynamic arguments from about 1850 disposed of those hypotheses about the interaction of matter and light which did not consider the conservation of energy. Similarly thermodynamics also falsified traditional solar theories; the theories which replaced them provided a firmer interpretation of the solar spectrum and consequently of spectra generally. The development of thermodynamics therefore placed the study of spectra and stare on a secure theoretical basis, not previously enjoyed. 3 CONTENTS page List of illustrations 5 Acknowledgements 7 Chapter 1 The physical interpretation of the undulatory theory of light 9 Chapter 2 Experiments o, and observations 21 of, emission and absorption spectra t 1830 Chapter 3 The debate on the nature of 44 absorption 1830-1835 and its chemical consequences Chapter 4 The study of spark spectra 85 1835- 1859 Chapter 5 The conservation of energy, 120 theories of spectra and resonating molecules 1851-1854 Chapter 6 The conservation and dissipation 148 of energy, and solar theories 1846-1862 Chapter 7 Spectro-chemical analysis 175 1854- 1861 Conclusion The early historiography of 207 spectroscopy Appendix The mathematical proof of 220 Kirchhoff's law of radiation 4 Contents (cont,) page Notes and references 222 to Chapter 1 223 to Chapter 2 230 to Chapter 3 238 to Chapter 4 247 to Chapter 5 256 to Chapter 6 268 to Chapter 7 279 to the Conclusion 291 Bibliography 1 Manuscripts 293 Bibliography 2 Printed sources 295 Erratum. For Waterson read Waterston 5 LIST OF ILLUSTRATIONS Cbapter 2 Fig. 1 Fraunhofer's apparatus to obtain facing p25 homogeneous light of different colours Fig. 2 Fraunhofer's illustration of p25 his samples of homogeneous light Fig. 3 Fraunhofer's solar spectrum facing p27 Fig. 4 Herschel's spectrum of light p32 transmitted through blue glass Fig. 5 Herschel's diffraction spectrum p41 Fig. 6 Young's diffraction spectrum p42 Chapter 3 Fig. 1 HerschePs sound interference p57 pipes Fig. 2 Wrede's reflecting surfaces p64 Fig. 3 Wrede's spectral map facing p66 Fig. 4 Wrede's spectrum of iodine p67 Fig. 5 W. A. Miller's spectra of facing p80 light transmitted through various gases and vapours Fig. 6 W. A. Miller's spectra of p81 coloured flames CIapter 4 Fig. 1 Wheatstone's apparatus to facing p87 measure the velocity of electricity Fig. 2 Wheatstorie's spark spectra p89 of various metals Fig. 3 Masson's spark spectra of facing plo2 various metals Fig. 4 ngstrm's atmospheric spectra facing plo8 Fig. 5 .ngstr3m's spark spectra of facing plo9 various substances 6 List of illustratiqns (cQnt.) Chapter 5 Figs. 1 & 2 Stokes's experiment to confirm p126 his idea of the causal agent of fhorescence Fig. 3 Kelvin's experiment to confirm p143 the identical refrangibility of the R and D lines Chapter 7 Fig. 1 Kirchhoff's aragonite apparatus facing pl82 Fig. 2 Kirchhoff' s spectroscopic p187 apparatus with which he first observed reversal Fig. 3 Kirchhoff's second (terrestrial) p188 experiment tQ display reversal Fig. 4 Kirhhoff's system of plates used p193 to prove his radiation law Fig. S Bunsen and Kirchhoff's spectral facing pl9g maps Fig. 6 Crookes s map of the thallium p204 spectrum Footnotes to Chapter 2 Fig. 1 Wollaston's solar spectrum p231 7 ACKNOWLEDGEMENTS I wish to thank my supervisor Dr. Marie Boas Hall for every encouragement and criticism during the writing of this thesis. I also thank Professor A. Rupert Hall for his help. I thank Mrs. Magda Whitrow for employing me as an assistant editor on volumes four and five of the "ISIS Cumulative Bibliography" during the first two years of my research. I thank the University of London for providing me with a research scholarship for the following two years and for a travelling scholarship to Germany. I wish to thank Professors G J. Whitrow (Imperial College), D. Cardwell (UMIST), A. J. Meadows (University of Leicester), Drs. N. Smith (Imperial College), G. Cantor (University of Leeds), C. Smith (University of Kent), M. Sutton (Newcastle Polytechnic), K. Dawson (Imperial College), B. Bowers (Science Museum, London), D. B. Wilson (Iowa State Uniyersity), D. Roos (North-Western University), J. Burchfield (Northe'n Illinois University), J. Paradis (MIT), Messrs J, T. LLoyd (University of Glasgow), and N. Lingard (Mancheste Polytechnic) for discussions and assistance on various topics within this thesis. I also thank Mrs Felicity Secretan and Mrs Gunnel Ingham for help with and translations from German and Swedish respectively. I also wish to thank members of the now defunct Department of History of Science and Technology, Imperial College, for their help. also thank Mrs. Frances De Marion de Glatigny for preparing the line drawings and Miss Heather Stanley for typing the manuscript. I gratefully acicnowjedge the help and assistance provided by the archivists and staffs of the following institutions. In England: Cambridge University Library, Royal Society Library, Imperial College, King's College London, University College London, Royal Society of Chemistry, Science Museum London, Public Record Office Kew, Principal Registry of the Family Division of the High Court, Royal Greenwich Observatory Hurstmonceux, 8 The National Trust at Lacock Abbey, and Williams (Hounslow) Ltd. In Scotland: Glasgow University Library, Department of Natural Philosophy Glasgow University, St. Andrews University Library, Edinburgh University Library, The National Library of Scotland and the Scottish Record Office. In Germany: Heidelberg University and the Deutsches Museum Munich. I thank the librarians and staffs of the following libraries for use of their facilities. At Imperial College: The Lyon Playfair Library (especially Miss G. !slcGurk and Miss J. Lewis of inter-library loans for finding the locations of so much obscure material); the libraries of the Chemistry, Mathematics, Physics, and Chemical Engineering departments and the Haldane Library. The libraries of the following institutions: The Science Museum, Victoria and Albert Museum, The Natural History Museum, The University of London, The Royal Society, The Royal Astronomical Society, Cambridge University and the British Museum. And, finally, I thank my parents for all forms of support and I dedicate this thesis to them. 9 Chapter One ThE PHYSICAL INTERPRETATION OF ThE UNDULATORY ThEORY OF LI(}!T That the undulatory theory Cof light] is defective as a physical representation of the phaenomena of light, has been admitted by the more candid of its supporters (1) With this statement written in 1833 David Brewster (2) summed up his fundamental objection to the undulatory theory of light and thereby touched off a sharp reaction from those people who did believe in the physical validity of the theory. Thus C. B. Airy (3), then Plumian Professor of Astronomy at Cambridge, had some very strong words to say both in public (4) and in private about the whole of Brewster's attitude towards the undulatory theory: Apropos of optics - I have just been looking at some numbers of Brewster's journal which I had not seen before: also at his new book. My estimation of Brewster has sensibly dropped. What an insolent fellow he is, on the strength of experiments Which are very valuable but which he does not know how to interpret (for nothing can be more awkward than his theories) to set about abusing the rest of the world in that way. There are many persons at Cambridge who understand the subject much better than he does, though they have made few experiments. There is also a hopeful proteg of Brewster's, Mr. R. Potter, who has made some good measures (apparently) and excells in this as if he had settled the whole theory of optics. Really these gentlemen of the northern school ought to be taught better (5). The reason why Brewster, who, as Airy had indicated, was highly esteemed as an experimentalist, produced such an effect on people like Airy who supported the undulatory theory was that he had deliberately touched on one of the weakest points of the undulatory theory - its lack of physical validity.