8 PHYSICAL SCIENCE 



led to a more careful consideration of the funda- 

 mental conceptions of natural science in general 

 by experimental and mathematical physicists. 



In more recent years fundamental changes of 

 outlook have been made by the recondite re- 

 searches of Bertrand Russell and A. N. White- 

 head, and the less mathematical writings of 

 C. D. Broad. 



In the following pages an attempt will be 

 made first to consider the philosophic foundations 

 of physics, and then to trace some of the more 

 important developments of the experimental in- 

 vestigations for which the last few years have 

 been remarkable. 



The study of physical equilibrium — the equi- 

 librium between different states or phases, solid, 

 liquid, and gaseous, of the same substance — 

 naturally opens with the consideration of the 

 relations between the different states of pure 

 chemical elements and compounds. Here, the 

 most striking work is the liquefaction of air 

 and hydrogen, with which the name of Dewar 

 most prominently must be associated. 



Next we turn to mixtures, and the fusion 

 and solidification of solutions and alloys claim 

 our attention. The microscopic analysis of 

 metals, when elucidated by the theory of equi- 

 librium, has had far-reaching influence on the 

 applied arts of metallurgy. 



Then are considered the problems of solution 

 in general, without restriction to conditions of 

 equilibrium. Now, for the first time, we come 

 in contact with electrical phenomena ; and the 

 theory of ionic conduction throws light, not only 



