ON THE PHYSICAL VIEW oK NATrRE. 189 



the ions, and how, during Llie process, wandering atoms 

 gave up or lost a definite something — viz., their electrical 

 charges. It seemed impossible in this cose to do without 

 an atomic or molecular view of electricity. Accordingly, 

 Helmlioltz, in his celebrated Faraday Lecture (1881), 

 after Iiaving traced the gradual displacement of the 

 Weberian theory of electrical particles acting at a 

 distance by that of Faraday, feels himself constrained 

 to say: "I see very well that the assumption of two 

 imponderable fluids of opposite ([ualities is a rather 

 complicated and artificial machinery, and that the 

 mathematical language of Clerk ^Maxwell's theory ex- 

 presses the laws of the phenomena very simply and 

 very truly ; . . • but I confess I should really ])e at a 

 loss to explain . . . what he considers as a quantity 

 of electricity, and why such a quantity is constant, like 

 that of a substance." And further on he says : " If we 

 accept the hypothesis that the elementary substances 

 are composed of atoms, we cannot avoid concluding 

 that electricity also ... is divided into definite 

 elementary portions, which behave like atoms of elec- 

 tricity." 



Besides the phenomena of chenucal decomposition, :>*■ 



^ '■ Modem 



there was another very large and important class of f'cctncai 



•JO I researchcj. 



phenomena which gradually led up to the conception 

 of the substantial and atomic nature of electricity. 

 This province of independent, and for a long time 

 isolated, research was opened out by the coml)ined 

 genius of PlUcker and Geissler. It was in tiic year 

 1857, two years before the announcement of tlie dis- 

 covery of spectrum analysis, that Pliicker, with the 



