ENERGY AND ITS TRANSFORMATIONS. 



5 



sphere of operation which is fully within the reach of 

 our senses; that the second class of forces is also, to a 

 certain extent, familiar to us through a knowledge of 

 their effects: but the last of these several classes of 

 forces existing in nature is, as yet, quite beyond our 

 ken. 



Studying these forms of manifestation of force which 

 are divided between the first two classes, we perceive a 

 distinction which is as well defined as is the line sepa- 

 rating the two classes of phenomena to which they give 

 rise. 



(i) Th.Q physical forces — and it is intended here to in- 

 clude the mechanical and chemical, as well as the forces 

 which are usually alone treated of in works on physics — 

 are capable of being observed, of being distinguished 

 by certain readily defined qualities, and of being ac- 

 curately measured quantitatively. The conditions which 

 lead to their active display are capable of being ex- 

 actly ascertained, and the precise results of their opera- 

 tions under any given set of conditions may usually be 

 accurately predicted. These conditions are subject to 

 certain definite modifications by the power of man, 

 and the changes of effect which will result from such 

 changes of condition may be predicted. The efTects 

 which nature produces in certain cases by the action of 

 these forces may be modified by man without entirely 

 defeating the original tendency to bring about a certain 

 change of mode of action of existing energy. These 

 forces, acting alone, never give rise to the more intri- 

 cate forms seen in nature. Their highest product in 

 the whole morphological range is a crystal of more or 

 less perfect shape, but of a form which is always of 

 some simple geometrical class. These forces do not 



