ON THE PHYSICAL VIEW OF NATURE. 153 



considered as the founders of the modern science of 

 physical chemistry, which has received an elaborate ex- 35. 



Ostwald'* 



position in the great work of Professor Ostwald. This physical 



chemistry. 



work is probably quite as epoch-making in the domain of 

 chemistry as Thomson and Tait's ' Natural Philosophy ' 

 has been in that of physics. 



I have already explained how in the development of 

 chemistry the attention of its great representatives was 

 almost entirely absorbed in gaining a knowledge of the 

 different substances with which they had to deal, and 

 how through preoccupation with the natural history of 

 matter, its decomposition, analysis and synthesis, and 

 appropriate classification, the other more scientific ques- 

 tions regarding the physical agencies which were at 

 work in chemical processes constituting the doctrine 

 of chemical affinity were almost completely neglected. 

 This I traced largely to the influence of that powerful 

 instrument of exact research, the atomic view, which 

 had been introduced into chemical science through 

 Lavoisier and Dalton. 1 The pursuit of physical chem- 



1 It is not an unusual experience 

 to find that the change from one 

 theory to another, though an ad- 

 vance from disproved to more cor- 

 rect views, is also accompanied by 

 some loss either in defiuiteness or 

 in actual knowledge of facts. The 

 undulatory theory lost the definite 

 notion of a rectilinear ray of light, 

 which was only regained by pro- 



pened when the older phlogiston 

 theory was dispelled by the atomic 

 theory and all attention was con- 

 centrated upon change of weight. 

 The older theory maintained that 

 when a metal is calcined it loses 

 something viz., phlogiston ; the 

 new theory had proved that it gains 

 something i.e., weight in the form 

 of combined oxygen. More recent 



longed and difficult analysis ; the | knowledge has shown that both 



electro-magnetic theory of Maxwell 

 has not as yet given a clear repre- 

 sentation of those electrical charges 

 which the older theory of Coulomb 

 and Weber introduced in the form 

 of stationary or moving electrical 

 masses. Something similar hap- 



theories are right. It gains weight 

 and loses potential energy, or power 

 to do work i.e., to combine, giv- 

 ing rise to molecular motion or 

 heat. The phlogiston theory con- 

 tained the correct idea that besides 

 matter there is something else 



