Manchester Memoirs, Vol. lit. (1908), No. 10. 23 



the new terminology of electric ions. It must have 

 presented itself from the first to the mind of any atomist 

 who was daring enough, in defiance of Faraday's own 

 express caution, to transcend the limits of experimental 

 observation, that here we have to do somehow with 

 electric atoms, and that the essence of chemical change 

 is involved in the passage of these entities across from 

 molecule to molecule. Maxwell contemplated but shrank 

 from making this plunge, being in fact fully occupied in 

 a more accessible and equally fundamental subject, the 

 mode of transmission and propagation of electrical in- 

 fluence; it was Helmholtz, further removed and thus not so 

 much under Faraday's direct influence, who in his Faraday 

 lecture to the Chemical Society of London in 1881* and 

 elsewhere, first marshalled systematically the evidence 

 that electricity must be atomic, and that the main energies 

 of chemical affinity are, as Faraday held, of electric type. 

 More recently the electron, or electric atom, has become 

 a necessary idea for electrodynamic theory, if that 

 is to include the origin of electric disturbance as well as 

 its mode of propagation. At first the view was natural 

 that the electron could be transferred only during the 

 intimate encounter of molecules, and so could hardly exist 

 free : though Helmholtz had enforced the idea that 

 electric excitation by friction consisted in the rending of 

 the molecules into material ions by the mutual forces 

 arising on the intimate contact between dissimilar sub- 

 stances thereby produced, and later investigations have 

 been concerned with traces of the same kind of phenomenon 

 appearing in chemical reactions such as ionisation of air 

 by phosphorus. The great experimental discoveries of 



* " On the modern development of Faraday's conception of Electricity," 

 "Wissen. Abhandl.,"ii., pp. 52-87. Cf. Faraday, "Experimental Researches 

 in Electricity," vol. L, No. 852, 871. 



