234 POPULAR LECTURES AND ADDRESSES. 



of chemical science, St. Clair Deville arrived at 

 his grand theory of dissociation without the 

 slightest aid from the kinetic theory of gases. 

 The fact that he worked it out solely from 

 chemical observation and experiment, and ex- 

 pounded it to the world without any hypothesis 

 whatever, and seemingly even without conscious- 

 ness of the beautiful explanation it has in the 

 kinetic theory of gases, secured for it immediately 

 an independent solidity and importance as a 

 chemical theory when he first promulgated it, to 

 which it might even by this time scarcely have 

 attained if it had first been suggested as a 

 probability indicated by the kinetic theory of 

 gases, and been only afterwards confirmed by 

 observation. Now, however, guided by the views 

 which Clausius and Williamson have given us of 

 the continuous interchange of partners between 

 the compound molecules constituting chemical 

 compounds in the gaseous state, we see in 

 Deville's theory of dissociation a point of con- 

 tact of the most transcendent interest between the 

 chemical and physical lines of scientific progress. 



