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Corpuscles, Electrons and Cathode Rays: J.J. Thomson and the ‘Discovery of the Electron’

Published online by Cambridge University Press:  05 January 2009

Isobel Falconer
Isobel Falconer
Affiliation:
Flat 3, Woodlands, Bridge Road, Leigh Woods, Bristol BS8 3PB, U.K.
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Extract

On 30 April, 1897, J. J. Thomson announced the results of his previous four months' experiments on cathode rays. The rays, he suggested, were negatively charged subatomic particles. He called the particles ‘corpuscles’. They have since been re-named ‘electrons’ and Thomson has been hailed as their ‘discoverer’. Contrary to the accounts of most later writers, I show that this discovery was not the outcome of a concern with the nature of cathode rays which had occupied Thomson since 1881 and had shaped the course of his experiments during the period 1881–1897. An examination of his work shows that he paid scant attention to cathode rays until late 1896.

Type
Research Article
Information
The British Journal for the History of Science , Volume 20 , Issue 3 , July 1987 , pp. 241 - 276
Copyright
Copyright © British Society for the History of Science 1987

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References

This paper is condensed from my Ph.D thesis ‘Theory and experiment in J.J. Thomson's work on gaseous discharge,’ University of Bath, 1985, in which further details may be found. I am grateful to my supervisor,David Gooding for encouragement and helpful criticism and to the University of Bath for financial support. I have enjoyed the hospitality of Oregon State University while writing this paper.

1 Thomson, J. J., ‘Cathode rays’ (Friday evening meeting of the Royal Institution, 30 April 1897), The Electrician, (1897), 39, p. 104.Google Scholar

2 For example, Anderson, D., The Discovery of the Electron, Princeton, N.J., 1964Google Scholar; Crowther, J. G., British Scientists of the Twentieth Century, London, 1952Google Scholar; Keller, A., The Infancy of Atomic Physics, Oxford, 1983Google Scholar; Price, D., ‘Sir J. J. Thomson OM, FRS’, Nuovo Cimento Supplement, (1957), 4, p. 1609CrossRefGoogle Scholar; 4th Rayleigh, Lord, The Life of Sir J. J. Thomson, Cambridge, 1942Google Scholar; Thomson, G. P., J. J. Thomson and the Cavendish Laboratory in his Day, Garden City, N. Y., 1964Google Scholar; Whittaker, E., A History of the Theories of Aether and Electricity: the Classical Theories, London, 1951.Google Scholar

3 Heilbron points this out in his DSB biography of Thomson. He takes an independent line from other writers [op. cit. (2)] and correctly emphasizes the importance of Thomson's commitment to Maxwell's electromagnetism and the mechanical philosophy in guiding the discharge work. However, he still assigns the cathode ray controversy unwarranted prominence. In particular, he sees the discovery of X-rays as an outcome of controversy rather than vice versa. Heilbron, J. L., ‘Thomson, Joseph John’, Dictionary of Scientific Biography, 13, p. 362.Google Scholar

4 Thomson, , op. cit. (1)Google Scholar; Thomson, J.J., ‘Cathode rays’, Philosophical Magazine (1897), V, 44, p. 293.Google Scholar

5 Larmor, J., ‘A dynamical theory of the electric and luminiferous medium’, Philosophical Transactions of the Royal Society, (1894), 185, p. 719CrossRefGoogle Scholar; (1895), 186, p. 695; (1897), 190, p. 205. Larmor first used the term ‘electron’ in 1894.

6 Lorentz, H. A., ‘La théorie électromagnetique de Maxwell et son application au corps mouvants’, Archives Neerlandaises, (1892), 25, p. 363.Google Scholar

7 McCormach, R., ‘H. A. Lorentz and the electromagnetic view of nature’, Isis, (1970), 61, p. 459.CrossRefGoogle Scholar

8 Throughout this paper I use the term ‘subatomic’ to signify not only the small size of the corpuscle but also its property of being an essential and universal constituent of atoms.

9 Thomson, , op. cit. (4) p. 313.Google Scholar

10 Ibid. Kelvin was reviving Boscovitchean ideas at this time, e.g., ‘Contact electricity and electrolysis according to Father Boscovitch’, Nature, (1897), 56, p. 84.Google Scholar

11 Thomson, , op. cit. (1), p. 108.Google Scholar

12 Thomson, J.J., Electricity and Matter, New York, 1904Google Scholar; The Corpuscular Theory of Matter, London, 1907.Google Scholar

13 For example, Anderson, , op. cit. (2)Google Scholar; Whittaker, , op. cit. (2).Google Scholar

14 One of the most complete traditional accounts of the controversy is given in Turpin, B., ‘The discovery of the electron: the evolution of a scientific concept 1800–1899’; Ph.D dissertation, University of Notre Dame, Indiana, 1980Google Scholar, Dissertation Abstracts International order no. 8020971. Turpin recognizes that Thomson was not much interested in cathode rays until 1896 but does not emphasize this enough. Nor does she go to the realization that virtually no-one in Britain was interested in cathode rays.

15 Crookes, W., ‘On radiant matter’, Nature, (1879), 20, p. 419.Google Scholar

16 For example, Goldstein, E., ‘On the electric discharge in rarefied gases’, Philosophical Magazine, (1880), V, 10, pp. 173, 234Google Scholar; (1882), V, 14, p. 366; Weidemann, E., ‘On the electric discharge in gases’, Philosophical Magazine, (1884), V, 18, pp. 35, 85.Google Scholar

17 Hertz, H., ‘Über Kathodenstrahlen’, Annalen der Physik und Chemie, (1883), 19, p. 782.CrossRefGoogle Scholar

18 Hertz, H., ‘Über den Durchgang der Kathodenstrahlen durch dunne Metallschichten’, Annalen der Physik und Chemie, (1892), 45, p. 28.CrossRefGoogle Scholar

19 Lenard, P., ‘Über Kathodenstrahlen’, Verhandlunger der Gesellschaft Deutsche Natforscher und Aerzte, (1893), 2, p. 36.Google Scholar ‘Über Kathodenstrahlen in Gasen von atmosphärischern Druck und im äussersten Vacuum’, Annalen der Physik und Chemie, (1894), 51, p. 225Google Scholar; ‘Über die magnetische Ablenkung der Kathodenstrahlen’, Annalen der Physik und Chemie, (1894), 52, p. 23.Google Scholar

20 Schuster, A., ‘The discharge of electricity through gases’ (Royal Society Bakerian Lecture), Proceedings of the Royal Society A, (1890), 47, p. 526.CrossRefGoogle Scholar

21 Thomson, J.J., ‘On the velocity of cathode rays’, Philosophical Magazine, (1894), V, 38, p. 358.Google Scholar

22 Perrin, J. ‘Nouvelles propriétés des rayon cathodiques’, Comptes Rendus, (1895), 121, p. 1130.Google Scholar

23 Thomson, J.J., ‘On the cathode rays’, Proceedings of the Cambridge Philosophical Society, (1897), 9, p. 243Google Scholar; op. cit. (1); op. cit. (3).

24 Kaufmann, W., ‘Die magnetische Ablenkbarkeit der Kathodenstrahlen und ihre Abhängigkeit vom Entladungspotential’, Annalen der Physik und Chemie, (1897), 61, p. 544CrossRefGoogle Scholar; (1897), 62, p. 596; Wiechert, E., ‘Ergebniss einer Messung der Geschwindigkeit der Kathodenstrahlen’, Schriften der physikalischökonomisch Gesellschaft zu Königsberg, (1897), 38, p. 3.Google Scholar

25 Kaufmann, W. and Aschkinass, E., ‘Über die Deflexon der Kathodenstrahlen’, Annalen der Physik und Chemie, (1897), 62, p. 588CrossRefGoogle Scholar; Lenard, P., ‘Über die electrostatischen Eigenschaften der Kathodenstrahlen’, Annalen der Physik und Chemie, (1898), 64, p. 279.CrossRefGoogle Scholar

26 Whittaker, , op. cit. (2), p. 351.Google Scholar

27 Anderson, , op. cit. (2), p. 29.Google Scholar

28 Goldstein, , op. cit. (16)Google Scholar; Wiedemann, , op. cit. (16).Google Scholar

29 I do not claim accuracy for these numbers as some sort of judgement had to be made as to whether papers represented a contribution to the controversy, or were merely concerned with the striking visual effects of cathode rays. The dividing line is fairly arbitrary. In addition, many contributions to Nature and The Electrician were indirect, contained in reports of meetings and editorial notices. Again, a judgement had to be made about how brief a report warranted inclusion. But the figure lists the original British contributions and the trend is very clear. The inclusion of all the minor notices would serve to exaggerate the peak of interest in 1896 without altering the numbers prior to 1896.

30 A detailed study of the German ether theories and attitude to the controversy is badly needed. Most accounts are written from the point of view of the winning particle theorists. The best account is Turpin, 's op. cit. (14).Google Scholar

31 Thomson, J.J., ‘On the electric and magnetic effects produced by the motion of electrified bodies’, Phil. Philosophical Magazine, (1881), V, 11, p. 229.Google Scholar

32 Thomson, J.J., Notes on Recent Researches in Electricity and Magnetism, Oxford, 1893Google Scholar, hereafter referred to as Recent Researches.

33 Cambridge University Library MS, Add 7654 NB36.

34 This difference between Schuster and Thomson was probably largely due to the conditions under which they performed their experiments. Neither quotes figures for the pressures they were working at, but Schuster appears to have expended more time in evacuating his apparatus. At the relatively high pressures of Thomson's experiments, cathode rays were not a significant phenomenon, but they probably were in Schuster's experiments. Schuster, A., ‘Experiments on the discharge of electricity through gases: a sketch of a theory’ (Royal Society Bakerian Lecture), Proceedings of the Royal Society, (1884), 37, pp. 317, 495CrossRefGoogle Scholar; ‘Experiments on the discharge of electricity through gases’, Proceedings of the Royal Society, (1887), 42, p. 371Google Scholar; ‘The passage of electricity through gases’, British Association Report, (1889), p. 510Google Scholar; ‘The disruptive discharge of electricity through gases’, Philosophical Magazine, (1890), V, 29, p. 182Google Scholar; op. cit. (20).

35 Thomson, , op. cit. (32), p. 121.Google Scholar

36 The Electrician, (1894), 33, p. 475.Google Scholar

37 FitzGerald, C., ‘On cathode rays in gases under atmospheric pressure and in extreme vacua’, The Electrician, (1894), 32, p. 573Google Scholar; ‘On Herr Lenard's experiments on the magnetic action of cathode rays’, The Electrician, (1894), 33, p. 151Google Scholar; Thomson, , op. cit. (21).Google Scholar

38 Schuster, , op. cit. (20).Google Scholar

39 As suggested by Keller, , op. cit. (2).Google Scholar

40 Becquerel, H., ‘Sur les radiations invisible émises par les corps phosphorescents’, Comptes Rendus, (1896), 122, p. 501.Google Scholar

41 Le Bon, , ‘La lumiere noire’, Comptes Rendus, (1896), 122, p. 188.Google Scholar

42 Batelli, Note in Nature, (1896), 54, p. 62.Google Scholar

43 Gifford, , ‘Are Röntgen rays polarised’, Nature, (1897), 54, p. 172.CrossRefGoogle Scholar

44 Vosmaer, and Ortt, , ‘Röntgen ray theory’, Nature, (1897), 56, p. 316.CrossRefGoogle Scholar

45 Lenard, P., ‘On cathode rays and their probable connection with Röntgen rays’, British Association Report, (1896), p. 709.Google Scholar

46 FitzGerald, G., ‘Review of Hertz's work’, Nature, (1896), 55, p. 7.Google Scholar

47 Stokes, G., ‘On the Röntgen rays’ (annual address to the Victoria Institute), Nature, (1896), 54, p. 427.Google Scholar

48 Thomson, J.J. ‘Presidential Address to Section A’, British Association Report, (1896), p. 194.Google Scholar

49 Thomson, J.J., The Discharge of Electricity Through Gases, New York, 1898, p. 194.Google Scholar

50 Rayleigh, , op. cit. (2), p. 133.Google Scholar

51 See works referenced in note (2). Heilbron [op. cit. (3)], however, correctly assesses Hertz's experiment as relatively unimportant.

52 FitzGerald, , op. cit. (43).Google Scholar

53 Sharlin, H., The Convergent Century: The Unification of Science in the Nineteenth Century, London, 1966Google Scholar; Wilson, D.B., ‘The thought of late Victorian physicists: Oliver Lodge's ethereal body’, Victorian Studies, (1971), 15, p. 29.Google Scholar

54 Larmor, , op. cit. (5), p. 719.Google Scholar

55 Klein examines the status of the mechanical philosophy and visualisable analogies, particularly Maxwell's use of them: Klein, M. J., ‘Mechanical explanation at the end of the nineteenth century’, Centaurus, (1972), 17, p. 58.CrossRefGoogle Scholar Topper has studied Thomson's commitment to mechanism in general, and to Maxwell in particular, in his thesis and two papers: Topper, D., ‘J. J. Thomson and Maxwell's Electromagnetic Theory’, Ph.D dissertation, Case Western Reserve University, 1970Google Scholar, University Microfilms order No. 71–19065; ‘Commitment to mechanism: J.J.Thomson, the early years’, Archive for the History of Exact Sciences, (1971), 7, p. 393Google Scholar; ‘To reason by means of images: J. J. Thomson and the mechanical picture of nature’, Annals of Science, (1980), 37, p. 31.Google Scholar The last of these is particularly important for containing details of Thomson's vortex analogies and the way he transposed them from one situation to another. However, Topper deals exclusively with Thomson's theoretical work. He does not consider any experimental stimulus for the theory changes he describes, nor the influence of these theoretical commitments on Thomson's experimental work. As Wheaton has pointed out, the mechanical philosophy was implicit in Thomson and Schuster's cathode ray experiments: they assumed that macroscopic mechanical laws carried over into the microscopic realm: Wheaton, B., The Tiger and the Shark, Cambridge, 1983, p. 6.CrossRefGoogle Scholar In my thesis and a forthcoming paper, I discuss other ways in which the mechanical philosophy influenced Thomson's approach to experiment: Falconer, I., ‘J. J. Thomson; an experimental genius?’ (1986)Google Scholar, submitted to Social Studies in Science.

56 Thomson, J.J., ‘On a theory of the electric discharge in gases’, Philosophical Magazine, (1883), V, 15, p. 427.Google Scholar

57 Thomson, J.J., ‘On the chemical combination of gases’, Philosophical Magazine, (1884), V, 18, p. 233Google Scholar; ‘The vortex ring theory of gases. On the law of the distribution of energy among the molecules’, Proceedings of the Royal Society, (1885), 39, p. 23.Google Scholar

58 Thomson, J.J., ‘Some experiments on the velocity of transmission of electric disturbances and their application to the theory of the striated discharge through gases’, Philosophical Magazine, (1890), V, 30, p. 129.Google Scholar

59 Thomson, J.J., ‘The relation between the atom and the charge of electricity carried by it’, Philosophical Magazine, (1895), V, 40, 511.Google Scholar

60 Thomson, J.J., Treatise on the Motion of Vortex Rings (Adams prize essay 1882), London, 1883.Google Scholar

61 Thomson, J.J. and Threlfall, R., ‘On an effect produced by the passage of an electric discharge through pure nitrogen’, Proceedings of the Royal Society, (1886), 40, p. 329CrossRefGoogle Scholar; ‘Some experiments on the production of ozone’, Proceedings of the Royal Society, (1886), 40, p. 340.Google Scholar

62 Thomson, J.J., ‘The electrolysis of steam’, Proceedings of the Royal Society, (1893), 53, p. 90CrossRefGoogle Scholar; ‘On the effect of electrification and chemical action on a steam jet, and of water on the discharge of electrodes from gases’, Philosophical Magazine, (1893), V, 36, p. 313Google Scholar; ‘The connection between chemical combination and the discharge of electricity through gases’, British Association Report, (1894), p. 482Google Scholar; ‘Electric discharge through gases’, Notices of Proceedings of the Royal Institution, (1894), 14, p. 239Google Scholar; ‘On the electricity of drops’, Philosophical Magazine, (1894), V, 37, p. 341Google Scholar; ‘On the electrolysis of gases’, Proceedings of the Royal Society, (1895), 58, p. 244Google Scholar; op. cit. (59).

63 Thomson, J.J., ‘A theory of the connection between cathode and Röntgen rays’, Philosophical Magazine, (1898), V, 45, p. 172Google Scholar; ‘On the connexion between the chemical composition of a gas and the ionisation produced in it by Röntgen rays’, Proceedings of the Cambridge Philosophical Society, (1898), 10, p. 10Google Scholar; ‘On the charge of electricity carried by the ions produced by Röntgen rays’, Philosophical Magazine, (1899), V, 47, p. 253Google Scholar; ‘The genesis of the ions in the discharge of electricity through gases’, Philosophical Magazine, (1900), V, 50, p. 278.Google Scholar

64 For example, Thomson, J.J., ‘On the passage of electricity through hot gases’, Philosophical Magazine, (1890), V, 29, p. 358Google Scholar; op.cit. (58).

65 Thomson, , op. cit. (58)Google Scholar; Recent Researches, op. cit. (32).Google Scholar

66 Peace, J., ‘On the potential difference required to produce a spark between two parallel plates in air at different pressures’, Proceedings of the Royal Society, (1892), 52, p. 99.CrossRefGoogle Scholar Peace was a research student at the Cavendish Laboratory.

67 Rutherford, E. and Thomson, J.J., ‘On the passage of electricity through gases exposed to Röntgen rays’, Philosophical Magazine, (1896), V, 42, p. 392.Google Scholar

68 Thomson, J.J., Recollections and Reflections, London, 1936, p. 325.Google Scholar

69 For example, Crowther, , op. cit. (2)Google Scholar; Price, , op. cit. (2)Google Scholar; Rayleigh, , op. cit. (2)Google Scholar; Thomson, G.P., op. cit. (2).Google Scholar

70 Rutherford, E., ‘1895–1898’, in A History of the Cavendish Laboratory 1871–1910, London, 1910, p. 159.Google Scholar

71 Cambridge University Library MS, Add 7654 NB39. My thesis contains a much more detailed account of this notebook and the evidence it contains of Rutherford and Thomson's theoretical expectations.

72 Thomson, J.J., ‘The Röntgen rays’, Nature, (1896), 53, p. 391.CrossRefGoogle Scholar

73 Thomson, J.J., ‘On the discharge of electricity produced by the Röntgen rays’, Proceedings of the Royal Society, (1896), 59, p. 391.Google Scholar

74 Thomson, J.J. and McClelland, J.A., ‘On the leakage of electricity through dielectrics traversed by Röntgen rays’, Proceedings of the Cambridge Philosophical Society, (1896), 9, p. 126.Google Scholar

75 Thomson, to Kelvin, , 10 04 1896Google Scholar, Cambridge University Library MS, Add 7342 T537.

76 Cambridge University Library MS, Add 7654 NB40. This notebook contains the notes for a series of lectures Thomson gave at Princeton in October 1896. The notes were probably written in August or September 1896, and represent an earlier viewpoint than the Thomson and Rutherford ionization paper, op. cit. (67). The lectures were published in 1898 as The Discharge of Electricity Through Gases, op. cit. (49), by which time Thomson had edited and revised them in the light of his recent cathode ray work.

77 The prevailing theory of magnetization was that suggested by Weber and subsequently developed by Maxwell and by Ewing. It supposed that a magnet consisted of small magnetic particles which were initially randomly oriented but became aligned under a magnetic force. Saturation occurred when all the particles were aligned.

78 Thomson, and McClelland, , op. cit. (74).Google Scholar

79 Op. cit. (71).

80 Rutherford, and Thomson, , op. cit. (67).Google Scholar

81 Thomson, , op. cit. (48).Google Scholar

82 Rutherford, , op. cit. (70).Google Scholar

83 For example, the notes for his Princeton lectures, op. cit. (76).

84 Rutherford verified this assumption in 1897: Rutherford, E., ‘The velocity and rate of recombination of the ions of gases exposed to Röntgen radiation’, Philosophical Magazine, (1987), V, 44, p. 422.Google Scholar

85 Ibid.

86 This tradition has been interpreted very well by Buchwald, J., From Maxwell to Microphysics, Chicago, 1985.Google Scholar

87 ‘Notes for lectures on electricity’ (c. 1886), Cambridge University Library MS, Add 7654 NB33 f5.

88 Thomson, J.J., ‘Some experiments on the electric discharge in a uniform electric field, with some theoretical considerations about the passage of electricity through gases’, Proceedings of the Cambridge Philosophical Society, (1886), 5, p. 391Google Scholar; ‘On the effect of pressure and temperature on the electric strength of gases’, Proceedings of the Cambridge Philosophical Society, (1889), 6, p. 325Google Scholar; ‘On the dissociation of some gases by the electric discharge’ (Royal Society Bakerian Lecture), Proceedings of the Royal Society, (1887), 42, p. 343Google Scholar; op.cit. (57).

89 Here, it may be significant that Napier Shaw, at the Cavendish, was compiling a report on electrolysis for the British Association in 1890: Shaw, W., ‘Report on the present state of our knowledge in electrolysis and electrochemistry’, British Association Report, (1890), p. 185.Google Scholar

90 Cambridge University Library MS, Add 7654 NB35a, f22.

91 Thomson, J.J., ‘On the illustration of the properties of the electric field by means of tubes of electrostatic induction’, Philosophical Magazine, (1891), V, 31, p. 150.Google Scholar

92 Ibid, p. 149.

93 Poynting, J.H., ‘On the transfer of energy in electromagnetic fields’, Philosophical Transactions of the Royal Society, (1884), 175, p. 343.CrossRefGoogle Scholar D. Topper has discussed the Faraday tube theory in great mathematical detail, emphasizing its place in mechanistic philosophy and Thomson's debt to Maxwell, , op. cit. (55).Google Scholar

94 Thomson, , op. cit. (91).Google Scholar

95 Blake, L., ‘Über Electricitätsenrwikelung bei der Verdampfung …’, Annalen der Physik und Chemie, (1883), 19, p. 518CrossRefGoogle Scholar; Sohncke, L., ‘Beitrage zur Theorie der Luftelectricität’, Annalen der Physik und Chemie, (1888), 34, p. 925.CrossRefGoogle Scholar Both these experiments showed that the vapours above electrically charged pools of liquid were uncharged.

96 Thomson, , op. cit. (58), (62), (64).Google Scholar

97 Thomson, , op. cit. (59).Google Scholar

98 Ibid. p. 513.

99 The mobilities of positive and negative ions were different, Thomson, , op. cit. (59).Google Scholar

100 Thomson, , op. cit. (60).Google Scholar

101 Op. cit. (90).

102 Mayer, A., ‘Floating magnets’, Nature, (1878), 17, p. 487.Google Scholar Thomson used this analogy again later to guide his corpuscular theory of the atom, long after he had abandoned the vortex atom. Thomson was not the only physicist to use Mayer's experiments as a guide for his atomic theory: see Snelders, H., ‘A.M. Mayer's experiments with floating magnets and their use in the atomic theories of matter’, Annals of Science, (1976), 33, p. 67.CrossRefGoogle Scholar

103 Op.cit. (90).

104 Owen, G., ‘The discovery of the electron’, Annals of Science, (1955), 11, p. 173.CrossRefGoogle Scholar

105 Thomson, and McClelland, , op. cit. (74).Google Scholar

106 Thomson, to Kelvin, , 10 04 1896Google Scholar, op. cit. (75).

107 Ibid.

108 Thomson, , op. cit. (73).Google Scholar

109 Thomson, to Kelvin, , 10 04 1896Google Scholar, op. cit. (75).

110 Thomson, J.J., ‘The Röntgen rays’, Nature, (1896), 53, p. 581.CrossRefGoogle Scholar

111 Op. cit. (76). These notes form the closest contemporary evidence for Thomson's views just before he began his cathode ray experiments.

112 Maier, C., ‘The role of spectroscopy in the acceptance of the internally structured atom’, Ph.D dissertation, Wisconsin, 1964.Google Scholar Dissertation Abstracts No. 64–10, 272.

113 Anderson, , op. cit. (2)Google Scholar; Thomson, G.P., op. cit. (2)Google Scholar; Turpin, , op. cit. (14)Google Scholar; and in Thomson's original papers, op. cit. (1), (4), (23).

114 Thomson, , op. cit. (23).Google Scholar

115 Thomson, , op. cit. (1).Google Scholar

116 Thomson, , op. cit. (4).Google Scholar

117 Cambridge University Library MS, Add 7653 NB4. See my thesis for a detailed discussion of the chronology of Thomson's electrostatic deflection experiments.

118 Lockyer, N., ‘Solar physics—the chemistry of the sun’, Nature, (1881), 24, pp. 267, 296, 315, 365, 391CrossRefGoogle Scholar; ‘On the chemistry of the hottest stars’, Proceedings of the Royal Society, (1897), 61, p. 148.Google Scholar

119 Maier, , op. cit. (112).Google Scholar

120 Lockyer, , (1897), op. cit. (118).Google Scholar

121 For an account of nineteenth century atomism see Knight, D.M., Atoms and Elements, London, 1967.Google Scholar For a good overview of late nineteenth century speculations about divisible atoms see Kragh, H., ‘Julius Thomsen and 19th century speculation on the complexity of atoms’, Annals of Science, (1982), 39, p. 37.CrossRefGoogle Scholar

122 Kragh, , op. cit. (121) p. 40.Google Scholar

123 Rayleigh, , op. cit. (2) p. 6.Google Scholar

124 Larmor, , op. cit. (5)Google Scholar; Lorentz, , op. cit. (6).Google Scholar

125 Royal Society MSS. RR12.160, RR13.207.

126 Rayleigh, , op. cit. (2).Google Scholar

127 Larmor remarked, in his first electron paper, that ‘free electrons’ could easily acquire velocities comparable with that of light; there might be a connection with cathode rays which, Thomson had told him, had velocities of about 2 × 10 cm/s: Larmor, , 1894, op. cit. (5), p. 813.Google Scholar

128 Here I am talking about the concept of charge that Thomson applied to his work on discharge. His theoretical work on electromagnetism was more sophisticated, see Buchwald, , op. cit. (86)Google Scholar for a discussion of this work.

129 Zeeman, P., ‘Over den invloed eener magnetische op den aard van het door een stof uitgezonden licht’, Verslagen en Medeelingen der Koninklijke Akademie van Wetenschappen, Amsterdam, (1896), 5, pp. 181, 242Google Scholar; ‘The effect of magnetisation on the nature of light emitted by a substance’, Nature, (1897), 55, p. 347.Google Scholar

130 Larmor, J., ‘The influence of a magnetic field on radiation frequency’, Proceedings of the Royal Society, (1897), 60, p. 514Google Scholar; Lodge, O., ‘The influence of a magnetic field on radiation frequency’, Proceedings of the Royal Society, (1897), 60, p. 513Google Scholar; ‘The latest discovery in physics’, The Electrician, (1897), 38, p. 568Google Scholar; ‘A few notes on Zeeman's discovery’, The Electrician, (1897), 38, p. 643.Google Scholar

131 Owen, , op. cit. (104).Google ScholarMaier, , [op. cit. (112)]Google Scholar and Turpin, [op. cit. (14)]Google Scholar follow Owen's account.

132 Thomson, J.J., ‘Carriers of negative electricity’ (Nobel lecture) in Les Prix Nobel en 1906, Stockholm, 1908Google Scholar; Heilbron, , op. cit. (3).Google Scholar

133 Thomson, G.P., op. cit. (2).Google Scholar

134 Maier, C., op. cit. (112)Google Scholar; Price, , op. cit. (2)Google Scholar; Rayleigh, , op. cit. (2).Google Scholar

135 Thomson, J.J., ‘On the existence of masses smaller than atoms’, British Association Report, (1899), p. 637Google Scholar; ‘On the masses of the ions in gases at low pressures’, Philosophical Magazine, (1899), V, 48, p. 547.Google Scholar

136 Kaufmann, , op. cit. (24)Google Scholar; Wiechert, , op. cit. (24).Google Scholar

137 Thomson, , op. cit. (1) 107Google Scholar; Zeeman, , op. cit. (129).Google Scholar

138 FitzGerald, G., ‘Dissociation of atoms’, The Electrician, (1897), 39, p. 103.Google Scholar

139 The term ‘electron’ was suggested to Larmor by FitzGerald [Buchwald, , op. cit. (86)Google Scholar]. Lodge, [op. cit. (130)]Google Scholar had shown how ‘free electrons’ would explain the Zeeman effect, but said that the idea originated with FitzGerald.

140 Lorentz to Thomson 1901. Cambridge University Library MS, Add 7654 L61.

141 ‘Electrical notes’, The Electrician, (1898), 40, p. 847.Google Scholar

142 For example, McClelland, J., ‘On the conductivity of gases from an are and from incandescent metals’, Proceedings of the Cambridge Philosophical Society, (1899), 10, p. 241Google Scholar; Rutherford, E., ‘The discharge of electrification by ultraviolet light’, Proceedings of the Cambridge Philosophical Society, (1898), 9, p. 401Google Scholar; Strutt, R., ‘On the behaviour of the Becquerel and Röntgen rays in magnetic field’, Proceedings of the Royal Society, (1900), 66, p. 75CrossRefGoogle Scholar; Thomson, , op. cit. (63 i)Google Scholar; Wilson, C.T.R., ‘On the condensation nuclei produced in gases by the action of Röntgen rays, uranium rays, ultraviolet light and other agents’, Philosophical Transactions of the Royal Society, (1899), 192, p. 403CrossRefGoogle Scholar; Wilson, H.A., ‘On the variation of the electric intensity and conductivity along the electric discharge in rarefied gases’, Philosophical Magazine, (1900), V, 49, p. 505.Google Scholar

143 Thomson, , op. cit. (135)Google Scholar.

144 Thomson, J.J., ‘Indications relatives à la constitution de la matiere’, Congres International de Physique. Rapports (Paris 1900), (1900), 3, p. 138Google Scholar; ‘The existence of bodies smaller than atoms’, Notices of Proceedings of the Royal Institution, (1901), 16, p. 138.Google Scholar

145 FitzGerald, , op. cit. (138), pp. 103–104.Google Scholar

146 Ibid.

147 The Electrician, (1897), 39, p. 735.Google Scholar

148 Swinton, A.C., ‘Studies in cathode and Röntgen radiation’, The Electrician, (1898), 41, pp. 246, 317.Google Scholar

149 For example, Kaufmann, , op. cit. (24)Google Scholar; Lenard, , op. cit. (25)Google Scholar; Wiechert, , op. cit. (24).Google Scholar

150 Two exceptions were Lockyer, [op. cit. (118)]Google Scholar and Elihu Thomson (no relation). Elihu Thomson had apparently been speculating about divisible atoms to explain some X-ray phenomena. He accepted Thomson's theory immediately, writing to The Electrician in 07 1897Google Scholar: ‘Since so eminent a physicist as Prof. J.J. Thomson has, in a recent paper, put forward the hypothesis of the breaking down of what we have been accustomed to call “the elements” and has shown a reasonable basis for such a hypothesis, the writer deems it not improper to state that a similar view had quite independently arisen in his own mind.’ [The Electrician, (1987), 39, p. 317].Google Scholar

151 The Electrician, (1897), 39, p. 299.Google Scholar

152 Milikan, R., The Electron: Its Isolation and Measurement…, Chicago, 1917Google Scholar; Townsend, J., ‘The diffusion of ions into gases’, Philosophical Transactions of the Royal Society, (1900), 193, p. 129CrossRefGoogle Scholar; Wilson, H.A., ‘A determination of the charge on the ions produced in air by Röntgen rays’, Philosophical Magazine, (1903), VI, 5, p. 429.Google Scholar

153 Kaufmann, , op. cit. (24)Google Scholar; Kaufmann, and Aschkinass, , op. cit. (25)Google Scholar; Kaufmann, W., ‘Die magnetische und electrische Ablenbarkeit der Becquerelstrahlen und die scheinbare Masse der Electronen’, Göttingen Nachrichten,(1901), p. 143.Google Scholar

154 Professor of Physics at the University of Moscow.

155 ‘Bien que les travaux de J. J. Thomson soient plus nombreux que ne le sont ceux de W. Kaufmann et embrassent un plus grand nombre de phénomènes, non seulement explorés au point de vue experimentale, mai aussi élucides theoriquement, nos connaissances dan e domaine de physique n'auraient pas atteint en ce moment leur niveau actuel sans les recherches de W. Kaufmann.…’ (Oumoff to the Nobel Foundation 31 January 1904, Nobel Foundation archives).

156 ‘Les résultats de ces expériences ont conduit pour la premiere fois à la notion d'un corpuscle cathodique bien plus petit que l'atome d'hydrogene’, (P. and M. Curie to the Nobel Foundation 26 December 1904, Nobel Foundation archives).

157 ‘Ces conceptions théoriques ont recu diverses confirmations parmi lesquelles nous citerons les recherches recentes de Mr Kaufmann qui sont favorable a l'opinion que la mass des corpuscles négatifs émis par le radium (rayons β), est entierement de nature électromagnétique’, (ibid.).

158 Thomson, , op. cit. (31).Google Scholar

159 Thomson, , op. cit. (135).Google Scholar FitzGerald had in effect suggested this when postulating that cathode rays were ‘free electrons’, as had des Coudres with his ‘weightless convergent lines of force structure’ in the ether.

160 These developments are discussed in McCormach, , op. cit. (7).Google Scholar

161 Hacking, I., Representing and Intervening, Cambridge, 1983.CrossRefGoogle Scholar

162 McCormach points out the significance of this to Lorentz, who recast his theory to treat individual electrons, and was able to determine experimentally the velocity dependence of the electron mass. McCormach, , op. cit. (7), p. 475.Google Scholar