526 GEOLOGY 



shall include both matter and ether, and for this place the word "sub- 

 stance" seems suitable. 1 Using the term in this sense, natural philo- 

 sophy may be defined as the science which treats of energy and 

 substance. 



Physics is the science which treats primarily of energy; chemistry 

 is the science which treats primarily of matter. Thus physics con- 

 siders mainly the actions and transformations of energy through 

 matter and ether; and chemistry considers mainly the actions and 

 transformations of matter through energy. But since energy is mani- 

 fest to the senses only through matter, and since matter does not 

 exist without manifestations of energy, the relations of the two sci- 

 ences are very intimate. In any book upon either subject the treat- 

 ment constantly passes over to the other; indeed, energy and matter 

 are inseparable, one cannot be considered without the other. 

 Recently the relations between physics and chemistry have become 

 even closer by the rise of the intermediate science, physical chem- 

 istry. This science completely bridges the gap between the two and 

 unites them as a whole into the conjoint science of physics-chemistry, 

 which is the science of energy and substance. As thus defined, physics- 

 chemistry becomes a synonym of natural philosophy in its broad 

 sense. 



While physics and chemistry are really a single science, it is to 

 be repeated that the chief point of view of physics proper is that 

 of energy, and the chief point of view of chemistry proper is that of 

 matter. This will be appreciated if one but mention the subjects 

 considered in text-books of physics and chemistry. Some of the 

 subjects of physics are sound, heat, light, and electricity. These 

 are all forms of energy. The chief subjects for consideration by 

 chemistry are the elements and their combinations, such as helium, 

 chlorine, iron, calcium-carbonate, etc. These are all forms of matter. 

 Since physics-chemistry treats of all the energy and substance 

 within the reach of our senses, physics and chemistry are the two 

 sciences the principles of which are believed to be applicable to the 

 entire visible universe. 



Astronomy treats of energy and substance in the heavens. It is 

 concerned primarily with the nature and development of the heavenly 

 systems. Under the above definition, astronomy is the science of 

 the physics and chemistry of the heavens. Biology treats of energy 

 and substance in living organisms. Under this definition, biology 

 is the science of the physics and chemistry of organisms. Geology 

 treats of the energy and substance of the earth. Under this definition, 



1 This definition of the word "substance" is different from that of Holman, 

 who, as I understand it, makes the term so comprehensive as to include matter, 

 ether, and energy. By him the word "matter" is apparently used to comprise 

 what is here covered by both matter and ether. See Silas W. Holman, Matter, 

 Energy Force and Work, p. 135 ff. 



