40 THE ADVANCE OF SCIENCE 



achieve- er moment than any other has to show, 



in Gilts 



Doc- advisedly ; and I think that there are 



(i) in mo-° f three great products of our time which 



constitu- i ust ^y tk e assertion. One of these is that 



tion of doctrine concerning the constitution of 



matter, 



(2) con- matter which, for want of a better name, 



scrvci- 



tion of I will call ' molecular ; ' the second is the 

 (sfevaLu- doctrine of conservation of energy ; the 

 tion. third is the doctrine of evolution. Each 

 of these was foreshadowed, more or less 

 distinctly, in former periods of the his- 

 tory of science ; and, so far is either from 

 being the outcome of purely inductive 

 reasoning, that it would be hard to over- 

 rate the influence of metaphysical, and 

 even of theological, considerations upon 

 the development of all three. The pe- 

 culiar merit of our epoch is that it has 

 shown how these hypotheses connect a 

 vast number of seemingly independent 

 partial generalisations ; that it has given 

 them that precision of expression which 

 is necessary for their exact verification; 



