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

  • Isobel Falconer (a1)

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.

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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.

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

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.

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

5 Larmor, J., ‘A dynamical theory of the electric and luminiferous medium’, Philosophical Transactions of the Royal Society, (1894), 185, p. 719; (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.

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

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.

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.

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

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

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

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, 1980, 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.

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

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

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

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

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

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

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

23 Thomson, J.J., ‘On the cathode rays’, Proceedings of the Cambridge Philosophical Society, (1897), 9, p. 243; 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. 544; (1897), 62, p. 596; Wiechert, E., ‘Ergebniss einer Messung der Geschwindigkeit der Kathodenstrahlen’, Schriften der physikalischökonomisch Gesellschaft zu Königsberg, (1897), 38, p. 3.

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

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

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

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

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).

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.

32 Thomson, J.J., Notes on Recent Researches in Electricity and Magnetism, Oxford, 1893, 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, 495; ‘Experiments on the discharge of electricity through gases’, Proceedings of the Royal Society, (1887), 42, p. 371; ‘The passage of electricity through gases’, British Association Report, (1889), p. 510; ‘The disruptive discharge of electricity through gases’, Philosophical Magazine, (1890), V, 29, p. 182; op. cit. (20).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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).

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

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

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. 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, 1970, 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. 393; ‘To reason by means of images: J. J. Thomson and the mechanical picture of nature’, Annals of Science, (1980), 37, p. 31. 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. 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), 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.

57 Thomson, J.J., ‘On the chemical combination of gases’, Philosophical Magazine, (1884), V, 18, p. 233; ‘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.

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.

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

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

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. 329; ‘Some experiments on the production of ozone’, Proceedings of the Royal Society, (1886), 40, p. 340.

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

63 Thomson, J.J., ‘A theory of the connection between cathode and Röntgen rays’, Philosophical Magazine, (1898), V, 45, p. 172; ‘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. 10; ‘On the charge of electricity carried by the ions produced by Röntgen rays’, Philosophical Magazine, (1899), V, 47, p. 253; ‘The genesis of the ions in the discharge of electricity through gases’, Philosophical Magazine, (1900), V, 50, p. 278.

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

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

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. 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.

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

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

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

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.

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

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.

75 Thomson, to Kelvin, , 10 04 1896, 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).

79 Op. cit. (71).

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

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

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

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.

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

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. 391; ‘On the effect of pressure and temperature on the electric strength of gases’, Proceedings of the Cambridge Philosophical Society, (1889), 6, p. 325; ‘On the dissociation of some gases by the electric discharge’ (Royal Society Bakerian Lecture), Proceedings of the Royal Society, (1887), 42, p. 343; 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.

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.

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. 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).

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

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

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

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

98 Ibid. p. 513.

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

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

101 Op. cit. (90).

102 Mayer, A., ‘Floating magnets’, Nature, (1878), 17, p. 487. 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.

103 Op.cit. (90).

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

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

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

107 Ibid.

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

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

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

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. Dissertation Abstracts No. 64–10, 272.

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

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

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

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

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, 391; ‘On the chemistry of the hottest stars’, Proceedings of the Royal Society, (1897), 61, p. 148.

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

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

121 For an account of nineteenth century atomism see Knight, D.M., Atoms and Elements, London, 1967. 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.

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

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

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

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

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

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.

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) 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, 242; ‘The effect of magnetisation on the nature of light emitted by a substance’, Nature, (1897), 55, p. 347.

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

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

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

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

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

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

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

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

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

139 The term ‘electron’ was suggested to Larmor by FitzGerald [Buchwald, , op. cit. (86)]. Lodge, [op. cit. (130)] 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.

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. 241; Rutherford, E., ‘The discharge of electrification by ultraviolet light’, Proceedings of the Cambridge Philosophical Society, (1898), 9, p. 401; Strutt, R., ‘On the behaviour of the Becquerel and Röntgen rays in magnetic field’, Proceedings of the Royal Society, (1900), 66, p. 75; Thomson, , op. cit. (63 i); 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. 403; 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.

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

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

145 FitzGerald, , op. cit. (138), pp. 103104.

146 Ibid.

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

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

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

150 Two exceptions were Lockyer, [op. cit. (118)] 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 1897: ‘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].

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

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

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

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).

159 Thomson, , op. cit. (135). 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).

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

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.

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

  • Isobel Falconer (a1)

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