NATURE 



[December 13, 1917 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



Resonance Radiation and the Quantum Theory. 



Ix the Philosophical Magaoine for September, 1916, 

 Dr. Silberstein has' made an attempt to explain the 

 resonance radiation of iodine vapour on the basis of 

 classical dynamics by assuming that the resonator is 

 non-Hookean — i.e. that its restitutive elastic force is 

 not simply proportional to the displacement. On this 

 theory, the principal lines in the resonance series 

 should appear at constant frequency-intervals, and to 

 support this view Dr. Silberstein has given a tabular 

 statement of the frequencies and their differences, based 

 upon the work of Prof. R. W. Wood. A critical exam, 

 ination of the figures shows, however, that the fre- 

 quency-intervals are by no means constant, but have 

 a decided tendency to decrease on the long wave-length 

 side. This has, indeed, been remarked upon by Prof. 

 Wood himself (Phil. Mag., October, 1912). I find on 

 calculation that it is not the frequencies themselves, 

 but their square-roots, that show constant decrements 

 in the series. The following table, prepared from Prof. 

 Wood's data (loc. cit., p. 684) for the mercury green 

 line excitation, demonstrates this clearly : — 



I The constancy of the figures in the last column over 



twenty lines seems altogether too striking to be acci- 

 dental, and rather suggests an analogy with Moseley's 

 law for the high-frequency spectra of the elements, 

 according to which the square-roots of the frequencies 

 of the K and L characteristic radiations increase by 

 equal steps with the atomic number of the element — 

 that is, on Sir E. Rutherford's theory, with the charge 

 on the nucleus. If, in the same element, we imagine 

 a configuration (permanent or quasi-stable) of the atom, 

 in which the electrons revolve in successive concentric 

 rings, the effect of the nucleus and all the other elec- 

 trons on any one electron may be approximately repre- 

 sented by a single nucleus of proper equivalent charge ; 

 and a mechanism in which this equivalent charge, 

 corresponding with the successive electrons in the atom, 

 varies by successive equal steps would, on the quan- 

 tum theory, exhibit the phenomena of resonance radia- 



tion, as in the case of iodine vapour. It seems pos- 

 sible that this idea may find application in the fuller 

 development of Bohr's theory of spectral series. 



T. K. Chinmayam. 

 210 Bow-Bazar Street, Calcutta, October 15. 



An Optical Phenomenon. 



In addition to the accounts in Nature referred to 

 by Mr. J. W. Giltay in your issue of November 22, 

 the phenomenon mentioned by me in Nature of 

 October 18 had previously been far more fully described 

 by Dr. John Aitken in a paper " On a New Variety 

 of Ocular Spectrum" in the Journal of Anatomy and 

 Physiology, vol. xiii., p. 322 ; and, as stated in this 

 paper, the phenomenon noticed by Mr. C. Carus Wil- 

 son (Nature, October 25), when travelling by train 

 in a rear coupe compartment, was described by Prof. 

 Silvanus Thompson in the report of the British Asso- 

 ciation for 1877. Dr. Aitken experimented with rotat- 

 ing discs divided into about twenty-four sectors, white 

 and black alternately, and with endless bands of paper 

 with black bars painted across them. A convenient 

 way of viewing the apparent motion was to look at 

 a sheet of mottled paper, after looking at the rotating 

 disc or moving band, when the markings on the paper 

 appeared to move in a contrary direction to the excit- 

 ing impression. Though some of the mottlings seem 

 to flow past the others, it was found by Dr. Aitken 

 that a straight line drawn across "the spectral stream" 

 did not appear to be bent, as one might have supposed 

 would be the case. If, after viewing the rotating disc, 

 another similar disc or the drawing of a wheel is 

 looked at, the second disc or the wheel appears to 

 rotate in a contrary direction to the first ; but if the 

 second disc is larger than the first, or the spokes 

 of the wheel are extended to a greater size than the 

 rotating disc, " this extension will entirely destroy all 

 appearance of rotation, and the wheel will appear at 

 rest. Do not these last experiments suggest that the 

 seat of illusion i§ deeper than the retina?" 



C. J. P. Cave. 



December 3. 



i 



THE CONTROL OF THE NON-FERROUS 

 METAL INDUSTRIES. 



BEFORE the war the world's markets for the 

 majority of the non-ferrous metals were very 

 largely controlled by a group of German metal 

 companies engaged ■ primarily in buying metals 

 and acting as selling agents for producers. How 

 complete this control was few people knew. The 

 outbreak of war disclosed it in all its formidable- 

 ness. The most important of these concerns was 

 the Metallgesellschaft of Frankfort-on-the-Main. 

 This place was the centre of certain German finan- 

 cial interests which had combined to establish the 

 Metall Bank and the Metallurgische Gesellschaft. 

 In ©ne way or another this great organisation had 

 established financial interests in metal under- 

 takings, not only in Germany and Austria, but 

 also in the U.S.A., the United Kingdom, and 

 various parts of the British Empire. 



This enormously powerful group of companies 

 controlled the world's metal markets, of which 

 Frankfort became the centre. Their connections 

 with other undertakings and their ramifications 

 were exceedingly complicated and difficult to con- 

 trol. In some instances there was a direct finan- 

 cial connection ; in others the connection was 



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