On the Charge of Electricity carried by the Ions produced by Rontgen Rays. London: Philosophical Magazine and Journal of Science, 1898.

London:: Taylor and Francis, 1898., 1898. Series: The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Vol. XLVI, Fifth Series, July – December. 219 x 152 mm. 8vo. Pages 528-545. [Entire volume: [vii], [1], 576 pp.] 3 figs. Quarter black morocco, morocco corners, marbled boards, raised bands, gilt spine; rubbed. Ex library blind-stamps of the University of Chicago Library. Very good. "It was reserved for J. J. Thomson to discover the true nature of the cathode rays. In April 1897 he gave a public demonstration. in which he declared that cathode rays are composed of particles of sub-atomic proportions. At this stage, he had been unable to calculate the weight of the particles, but he had measured their rate of charge to mass. The ratio was large, so they must either have a big charge or a small mass. If the charge could be calculated, then the mass could be found, since the ratio between the two was known. Thomson eventually succeeded in calculating the charge, by an ingenious adaptation of the 'dust counter' devised by C. T. R. Wilson. By observing variations in their fall in various electric fields he was able to calculate the electric charge on the particles. These experiments. led to the calculation of the mass of the electron as one eighteen-hundredth of a hydrogen atom, hitherto the lightest known object. Moreover, the mass of these 'corpuscles', as Thomson called them, was constant, whatever their origin. That is to say that all forms of matter, no matter how varied their chemical composition, produced cathode rays of uniform make-up. The reference to 'Rontgen rays' in [the above article] indicates their identity with cathode rays" – Printing and the Mind of Man. / "What, precisely, did J. J. Thomson contribute to the discovery of the electron? Because the electron was "discovered" in 1897, one naturally takes this to be a question about what Thomson claimed pertaining to the electron during 1897, and hence a question about his April 30 Friday Evening Discourse on cathode rays at the Royal Institution,1 in which he ?rst put the subatomic proposal forward, and his subsequent classic paper "Cathode Rays" in the October issue of Philosophical Magazine.2 Restricting the question to 1897, however, gives one a seriously incomplete and consequently misleading answer to the question of what Thomson contributed. Further, it gives a picture of what he and his research students at the Cavendish Laboratory were up to at the time that they would have had trouble recognizing. Thomson's contribution to the discovery of the electron stretched over the next two years as well. His 1897 paper is the ?rst in a sequence of three equally classic Philosophical Magazine papers presenting fundamental experimental results on the electron: the second, "On the Charge of Electricity carried by the Ions produced by Rontgen Rays," appeared in December 1898,3 and the third, "On the Masses of the Ions in Gases at Low Pressures," in December 1899.4 The last ?ve pages of this 1899 paper put forward a new account of ionization and electrical conduction in gases. These ?ve pages culminated Thomson's e?orts on the electron." (p.22). / "The second paper, "On the Charge of Electricity carried by the Ions produced by Rontgen Rays," appeared in December 1898.78 It reports the results of an elaborate experiment for determining the charge e of the negative ions produced when x-rays pass through a gas. The relationship between these negative ions and Thomson's corpuscle is left an entirely open question throughout this paper. The basic idea behind the experiment is to infer the charge per ion from the amount of electricity (per unit area per unit time) passing through the ionized gas under an electromotive force. Assuming all ions have the same magnitude of charge, e, this quantity of electricity is simply neu, where n is the number of ions per unit volume and u is the mean velocity of the positive and negative ions under the electromotive force. The charge per ion can be thus be inferred from a determination of n and u. Three separate results published by Thomson's research students during 1897 opened the way to determining n and u." (pp. 45-6)." See: Histories of the Electron: The Birth of Microphysics edited by Jed Z. Buchwald and Andrew Warwick. Dibner Institute Studies in the History of Science and Technology. / Thomson received various honors, including the Nobel Prize in Physics in 1906 and a knighthood in 1908. (Inventory #: S14226)