60 



THE FROGRES- 



Physical science is one and indivisible. Alt! 

 for practical purposes, it is convenient t> mark it 

 out into the primary regions >t IMi\- 

 Chemistry, and Biology, and to subdivide these 

 into subordinate provinces, yet the method of 

 investigation and the ultimate object of the 

 physical inquirer are everywhere the same. 



The object is the discovery of tin- rational order 

 which pervades the universe ; the method cons 

 of observation and experiment (which is observa- 

 tion under artificial conditions) for the determina- 

 tion of the facts of Nature; of inductive and 

 deductive reasoning for the discovery of their 

 mutual relations and connection. The various 

 branches of physical science differ in the extent to 

 which, at any given moment of their hisr 

 observation on the one hand, or ratiocination on 

 the other, is their more obvious feature, but in 

 other way ; and nothing can be more incoi : 

 than the assumption one sometimes meets with, 

 that physics has one method, chemistry another, 

 and biology a third. 



All physical science starts from certain pos- 

 tulates. One of them is the objective existence 

 of a material world. It is assumed that the 

 phenomena which are comprehended under this 

 name have a " substratum " of extended, impene- 

 trable, mobile substance, which exhibits the quality 

 known as inertia, and is termed matter. 1 Another 

 1 I am aware that this proposition may be challenged. It 









