[41] See Radioactive Transformations (p. 251). Professor Rutherford says that "each of the alpha ray products present in one gram of radium product (sic) expels 6.2 x 1010 alpha particles per second." He also remarks on "the experimental difficulty of accurately determining the number of alpha particles expelled from radium per second."—ED.
[42] See Rutherford, op. cit. p. 150.—ED.
[43] This view of the case has been made very clear by M. Gustave le Bon in L'Évolution de la Matière (Paris, 1906). See especially pp. 36-52, where the amount of the supposed intra-atomic energy is calculated.—ED.
[44] This is the main contention of M. Gustave Le Bon in his work last quoted.—ED.
[45] See last note.—ED.
[46] In reality M. Sagnac operated in the converse manner. He took two equal weights of a salt of radium and a salt of barium, which he made oscillate one after the other in a torsion balance. Had the durations of oscillation been different, it might be concluded that the mechanical mass is not the same for radium as for barium.
[47] Many theories as to the cause of the lines and bands of the spectrum have been put forward since this was written, among which that of Professor Stark (for which see Physikalische Zeitschrift for 1906, passim) is perhaps the most advanced. That of M. Jean Becquerel, which would attribute it to the vibration within the atom of both negative and positive electrons, also deserves notice. A popular account of this is given in the Athenæum of 20th April 1907.—ED.
[48] An objection not here noticed has lately been formulated with much frankness by Professor Lorentz himself. It is one of the pillars of his theory that only the negative electrons move when an electric current passes through a metal, and that the positive electrons (if any such there be) remain motionless. Yet in the experiment known as Hall's, the current is deflected by the magnetic field to one side of the strip in certain metals, and to the opposite side in others. This seems to show that in certain cases the positive electrons move instead of the negative, and Professor Lorentz confesses that up to the present he can find no valid argument against this. See Archives Néerlandaises 1906, parts 1 and 2.—ED.
[49] This cannot be said to be yet completely proved. Cf. Sir Oliver Lodge, Electrons, London, 1906, p. 200.—ED.
[50] The reader should, however, be warned that a theory has lately been put forth which attempts to account for crystallisation on purely mechanical grounds. See Messrs Barlow and Pope's "Development of the Atomic Theory" in the Transactions of the Chemical Society, 1906.—ED.