598 CHARLES R. VAN HISE 



might lead to the conclusion that the subject of geology is reduced 

 to simpler terms than is really the fact. Each of the forms of energy, 

 gravitation, heat, elasticity, cohesion, chemical affinity, electricity, 

 magnetism, and radiation is most complex and acts as forces in 

 most diverse ways. The number of gases, of liquids, and of solids 

 which occur in nature are beyond number. They are most diverse 

 in character. For instance, the liquids vary from nearly pure water 

 to magma. The solids comprise all kinds of minerals, of which 

 there are many hundreds, and the various combinations of these 

 minerals in rocks, the different phases of which are very numerous. 

 Gas without the presence of liquids and solids, liquids without the 

 inclusion of gases and solids, and solids which contain no gases or 

 liquids, while perhaps possible in a physical or chemical laboratory, 

 are not found in nature. As remarked by Powell, gases, liquids, 

 and solids are everywhere commingled upon the earth. All are 

 commingled with ether. Thus the various combinations of agents 

 are beyond computation. Also definite agents, for instance water 

 may occur in various kinds of bodies, each of which acts in a manner 

 peculiar to itself. 



The materials upon which the agents act are of the same kinds, 

 and have the same diversities and complexities, as the agents them- 

 selves. Moreover, the work done inevitably affects both the mate- 

 rial acted upon and the agent. The agent that grinds the rock- 

 floor at the bottom of a glacier is also ground. This necessity of 

 work upon both agent and substance acted upon comes under the 

 law of Newton in reference to action and reaction. The fact of 

 work both upon agent and substance upon which the agent acts 

 raises the question as to the distinction between the two. The 

 answer is: The agent is the substance containing energy which it 

 expends in doing work upon other substances. The substance upon 

 which work is done may thereby receive energy, and thus become 

 an agent which does work upon other substances; and so on indefi- 

 nitely. Indeed, the rule is that one process follows another in the 

 sequence of events, until the energy concerned becomes so dispersed 

 as to be no longer traceable. Theoretically this goes on indefinitely. 



Analysis of geological processes. — We have seen that the action of 

 one or more agents through the exertion of force and the expenditure 



