THE PROBLEMS OF GEOLOGY 593 



was at first an observational study. The next step, a revolutionary 

 one, v^^as to explain the observed phenomena in terms of physical 

 and chemical processes, many of which could be observed. But few 

 have asked the question: "What is a geological process?" 



GEOLOGICAL PROCESSES. 



It is a curious fact that, while the word "process" is used in 

 innumerable geological papers and text-books, I have been unable 

 to find anywhere a definition of a "geological process." 



I shall define a "geological process" as the action of an agent 

 by the exertion of force involving the expenditure of energy upon 

 some portion of the substance of the earth. 



Physical definitions of ^^ force,'" ^'work," '' energy," and "agent." — 

 In order to understand the above definition of "geological process" 

 it is necessary to define the terms "force," "work," "energy," and 

 "agent." 



Hoskins defines "force" as action exerted by one body upon 

 another tending to change the state of motion of the body acted upon.^ 

 According to Daniell's more simple definition, "force" is any cause 

 of motion.^ 



When a force applied to a body moves the body in the direction 

 toward which the force acts, it does work.^ In this sense "work" is 

 the product of force into displacement, the common formula being 

 W = FS. The unit of work is defined as the quantity of work done 

 by a unit force acting through a unit distance. ^ 



Hoskins defines "energy" in the terms of force and work. Thus 

 he says when the condition of a body is such that it can do work 

 against a force or forces that may be applied to it the body is said to 

 possess energy. The unit of energy is the same as that of work.^ 

 According to Daniell's more simple definition, "energy" is the power 

 of doing work.^ 



The order of definition of the above terms is that in which knowl- 

 edge of them has developed. The actions of forces in doing work are 



1 T. M. Hoskins, Theoretical Mechanics, 1900, pp. 2 and 16. 



2 Alfred Daniell, A Text-book of the Principles of Physics, 3d ed. (1895), p. 4. 



3 Hoskins, op. cit., p. 298. 4 Ibid., p. 298. 



s Ibid., p. 308. . 6 Daniell, op. cit., p. 2. 



