[31] The whole of this argument is brilliantly set forth by Professor Lorentz in a lecture delivered to the Electrotechnikerverein at Berlin in December 1904, and reprinted, with additions, in the Archives Néerlandaises of 1906.—ED.
[32] In his work on L'Évolution de la Matière, M. Gustave Le Bon recalls that in 1897 he published several notes in the Académie des Sciences, in which he asserted that the properties of uranium were only a particular case of a very general law, and that the radiations emitted did not polarize, and were akin by their properties to the X rays.
[33] Polonium has now been shown to be no new element, but one of the transformation products of radium. Radium itself is also thought to be derived in some manner, not yet ascertained, from uranium. The same is the case with actinium, which is said to come in the long run from uranium, but not so directly as does radium. All this is described in Professor Rutherford's Radioactive Transformations (London, 1906).—ED.
[34] This is admitted by Professor Rutherford (Radio-Activity, Camb., 1904, p. 141) and Professor Soddy (Radio-Activity, London, 1904, p. 66). Neither Mr Whetham, in his Recent Development of Physical Science (London, 1904) nor the Hon. R.J. Strutt in The Becquerel Rays (London, same date), both of whom deal with the historical side of the subject, seem to have noticed the fact.—ED.
[35] It has now been shown that polonium when freshly separated emits beta rays also; see Dr Logeman's paper in Proceedings of the Royal Society, A., 6th September 1906.—ED.
[36] According to Professor Rutherford, in 3.77 days.—ED
[37] Professor Rutherford has lately stated that uranium may possibly produce an emanation, but that its rate of decay must be too swift for its presence to be verified (see Radioactive Transformations, p. 161).—ED.
[38] An actinium X was also discovered by Professor Giesel (Jahrbuch d. Radioaktivitat, i. p. 358, 1904). Since the above was written, another product has been found to intervene between the X substance and the emanation in the case of actinium and thorium. They have been named radio-actinium and radio-thorium respectively.—ED.
[39] Such a table is given on p. 169 of Rutherford's Radioactive Transformations.—ED.
[40] This opinion, no doubt formed when Sir William Ramsay's discovery of the formation of helium from the radium emanation was first made known, is now less tenable. The latest theory is that the alpha particle is in fact an atom of helium, and that the final transformation product of radium and the other radioactive substances is lead. Cf. Rutherford, op. cit. passim.—ED.