from Faraday to J . J . Thomson. 397 







In the theory of Weber, electric phenomena were attributed 

 to the agency of stationary or moving charges, which could 

 most readily be pictured as having a discrete and atom-like 

 existence. The conception of displacement, on the other hand, 

 which lay at the root of the Maxwellian theory, was more in 

 harmony with the representation of electricity as something 

 of a continuous nature; and as Maxwell's views met with 

 increasing acceptance, the atomistic hypothesis seemed to have 

 entered on a period of decay. Its revival was due largely to the 

 advocacy of Helmholtz,* who, in a lecture delivered to the 

 Chemical Society of London in 1881, pointed outf that it was 

 thoroughly in accord with the ideas of Faraday,J on which 

 Maxwell's theory was founded. " If," he said, " we accept the 

 hypothesis that the elementary substances are composed of 

 atoms, we cannot avoid concluding that electricity also, positive 

 as well as negative, is divided into definite elementary portions 

 which behave like atoms of electricity." 



When the conduction of electricity is considered in the 

 light of this hypothesis, it seems almost inevitable to conclude 

 that the process is of much the same character in gases as in 

 electrolytes ; and before long this view was actively maintained. 

 It had indeed long been known that a compound gas might be 

 decomposed by the electric discharge ; and that in some cases 

 the constituents are liberated at the electrodes in such a way 

 as to suggest an analogy with electrolysis. The question had 

 been studied in 1861 by Adolphe Perrot, who examined the 

 gases liberated by the passage of the electric spark through 

 steam. He found that while the product of this action was 

 a detonating mixture of hydrogen and oxygen, there was a 

 decided preponderance of hydrogen at one pole and of oxygen 

 at the other. 



The analogy of gaseous conduction to electrolysis was 

 applied by W. Giese,|| of Berlin, in 1882, in order to explain 



* Cf. also G. Johnstone Stoney, Phil. Mag., May, 1881. 



f Journ. Chem. Soc. xxxix (1881), p. 277. \ Cf. p. 200. 



Annales de Chimie (3), Ixi, p. 161. 



|| Ann. d. Phys. xvii (1882), pp. 1, 236, 519. 



