An apparently different quantum theory, due to de Broglie[20] and Schrödinger,[21] has been found to be formally the same as Heisinger's theory, although at first sight very different. This is described by de Broglie as "the new wave theory of matter," in which "the material point is conceived as a singularity in a wave."[22] Here, also, the radiations which we think of as coming out of the atom have more physical "reality" than the atom itself. One of the merits of the theory is that it diminishes the difficulties hitherto[Pg 47] existing in the way of a reconciliation of the facts of interference and dispersion with the facts which led to the hypothesis of light quanta. Meanwhile, there remains the possibility that all the quantum phenomena may be deducible from classical principles, and that the apparent discontinuities may be only a question of sharp maxima or minima. The most successful theory known to me on these lines is that of L. V. King.[23] He assumes that electrons rotate with a certain fixed angular velocity, the same for all; he makes a similar assumption as regards protons. Consequently there is a magnetic field which introduces conditions that are absent if electrons and protons have no spin. There will be electromagnetic radiation of frequency , where: being Planck's constant, the invariant mass of the electron, and its velocity. (The identity of with Planck's constant is obtained by adjusting the hypothetical constants.) From this formula he deduces many of the phenomena upon which the quantum theory is based, and promises to deduce others in a later paper. An article by Mr R. H. Fowler ("Spinning Electrons," Nature, Jan. 15, 1927) discusses Mr King's theory without arriving at a verdict for or against. Presumably it will not be long before a definite answer as to the adequacy of Mr King's theory is possible. If it is adequate, the quantum theory ceases to concern the philosopher, since what remains valid in it becomes a deduction from more fundamental laws and processes which are continuous and involve no atomicity of action. For the moment, until the physicists have arrived at a decision, the philosopher must be content to investigate both hypotheses impartially. FOOTNOTES: [7] The numerical value of is , and its dimensions are those of "action"—i.e. energy x time. [8] Report on Radiation and the Quantum Theory, Physical Society of London, 1914, p. 58. [9] Annalen der Physik, vol. XVII., p. 146. [10] See Jeans, loc. cit., chap. VI. [11] See Sommerfeld, Atomic Structure and Spectral Lines, pp. 547 ff. [12] W. Wilson, The Quantum Theory of Radiation and Line Spectra Phil. Mag., June, 1915. [13] What follows is taken from Note 7 (pp. 555 ff.) in Sommerfeld's Atomic Structure and Spectral Lines, translated from the third German edition by Henry L. Brose, M.A., 1923. See also Note 4 (pp. 541 ff.).