530 On Helmholtz's Electrochemical Theory. 



The equation that the centrifugal force is equal to the force 

 of attraction gives for the latter a value nearly equal to that 

 of the attraction of two " electrons " on each other. Further, 

 I put forward at the same time the hypothesis that radiation 

 is caused by the oscillations of the valency-charges. This 

 supposition was not new, as I have since found. His own 

 quotation in his book, 'Theorie der electrischen und optischen 

 Erscheinungen in bewegten Korpern/ Leiden, 1895, page 5, 

 called my attention to the fact that Prof. H. A. Lorentz as 

 early as 1878 attributed light-waves to electrical particles, 

 which are joined to the atoms and which are also assumed in 

 electrolysis \Verli. d. kgl. Akad. v. Wetenschappen, 18 Deel, 

 Amsterdam, 1879; notice especially the conclusion, page 112]. 

 Professor Hertz, as he told me, was of a similar opinion ; 

 however, he was not attached to the electrochemical theory 

 of Helmholtz, but to the opinion of Victor Meyer and Riecke 

 (Berliner Chem. Ber. xxi. p. 946, 1888). But Lorentz's 

 electromagnetic theorv of refraction is, like Helmholtz^s 

 theory of Dispersion (1892), independent of the size of the 

 valency-charges. From this quantity, the " electron," I have, 

 in my paper mentioned above of the 12th Jan. 1891, calcu- 

 lated that the period of rotation of the two atoms of a 

 molecule round one another is about 10~~ 14 seconds. This 

 is the period of the electrodynamic radiation which the 

 electrons of the two atoms give out while they rotate together 

 with the ponderable atoms round one another. It would 

 correspond with ultra-red waves. As the computed value of 

 the period of rotation is only the average value of the differ- 

 ent periods of rotation possessed at the same time by different 

 molecules, the emission must give a more or less extended 

 spectrum of dark heat-rays, which spectrum would have its 

 maximum in the region of the average value. Indeed emis- 

 sion of gases is similar, in so far as the latter is only based 

 on increase of temperature. When the period of rotation 

 is accelerated the spectrum might possibly pass into the visible 

 region. 



Prof. G. J. Stoney took up the matter of the electro- 

 dynamic radiation of oscillating electrons at about the same 

 time as I did, but in other respects (Trans. Roy. Dublin Soc. 

 vol. iv. 1891, p. 585) ; later also Prof. H. Ebert (Arch, 

 de Geneve, [3] xxv. p. 489, May 1891). 



I next developed the purely kinetic part of my conclusions 

 fWied. Ann. xlviii. March 1893, pp. 467-492). There I 

 have also taken into consideration the dissociation-heat of 

 hydrogen given by Prof. Eilhard Wiedemann. The same I 

 have also made use of for comparison, besides the dissociation- 



