ON THE PHYSICAL VIEW (XF NATURE. 153 



considered as the founders of the modern science of 

 physical chemistry, which has received an elaborate ex- Ostw 3 a ^, s 

 position in the great work of Professor Ostwald. This ^eiS-y 

 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- 



It is not an unusual experience | pened when the older phlogiston 



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 definiteness or 

 in actual knowledge of facts. The 

 undulatory theory lost the definite 



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 



notion of a rectilinear ray of light, | something i.e., weight in the form 



which was only regained by pro- ] of combined oxygen. More recent 



longed and difficult analysis ; the knowledge has shown that both 



electro- magnetic theory of Maxwell theories are right. It gains weight 



has not as yet given a clear repre- and loses potential energy, or power 



sen tation of those electrical charges to do work i.e., to combine, giv- 



which the older theory of Coulomb . ing rise to molecular motion or 



and Weber introduced in the form heat. The phlogiston theory con- 



of stationary or moving electrical ! tained the correct idea that besides 



masses. Something similar hap- matter there is something else 



