ORGANIZATION OF THE SCIENCES 



knowledge, outside of pure mathematics, which 

 has not undergone a veritable revolution. Mo- 

 lecular physics has been revolutionized by the 

 discovery of the correlation of forces ; and the 

 deduction of that principle, as well as of the 

 principle of virtual velocities, from the law of 

 the persistence of force, has placed molar phy- 

 sics also upon a new basis. Chemistry, as we 

 have seen, has undergone changes nearly as 

 sweeping as those brought about by Lavoisier ; 

 changes which have thoroughly renovated our 

 conceptions of the phenomenal constitution of 

 matter. Sidereal astronomy has been brought 

 into existence as a science ; and we have learned 

 how to make a ray of light, journeying toward 

 us from the remotest regions of space, tell us 

 of the molecular constitution of the matter from 

 which it started. Geology has been robbed of 

 its cataclysms and periods of universal extinc- 

 tion ; while both astrogeny and geogeny have 

 assumed a new character through the wide ex- 

 tension of the theory of nebular genesis. There 

 i«- not a truth in biology which has not been 

 shown up in a new light by the victory of the 

 cell-doctrine ; the discovery of natural selection 

 has entirely remodelled our conceptions of or- 

 ganic development ; and the dynamical theory 

 of stimulus has wrought great changes, which 

 are but the beginning of greater changes, in pa- 

 thology, in hygiene, and in the treatment of 



VOL. II 6^ 



