ENERGY IN GENERAL. 71 



moving. This burden is a weight that is to say, a 

 mass acted on by the force of weight Man resists 

 this force so as to prevent its effect. If it were not 

 annihilated by man's effort^ this effect would be the 

 motion or the fall of the heavy body. The effort and 

 the force are thus in equilibrium, and the effort is 

 equal and opposite to the force. It gives to the man 

 who exercises it the conscious idea of force. Thus we 

 know of force through effort. Every clear idea that 

 we can have of force springs from the observation of 

 our muscular effort. 



The notion of force is thus an anthropomorphic 

 notion. When an effect is produced in nature outside 

 human intervention, we say that it is by something 

 analogous to what in man is effort, and we give to this 

 something a name which is also analogous, namely 

 force. To give a name to effort and to compare 

 efforts in magnitude, we need not know all about 

 them, nor need we know in what they essentially 

 consist, of what series of physical, chemical, and 

 physiological actions they are the consequence. And 

 so it is with force. It is a resistance to motion or 

 the cause of motion. This cause of motion may be 

 an anterior motion (kinetic force). It may be an 

 anterior physical energy (physical and chemical 

 forces). 



Forces are measured in the C.G.S. system by com- 

 paring them with the unit called the Dyne. 1 In 

 practice they are compared with a much larger unit 

 the gramme, which is the weight, the force acting on 

 a unit of mass of one centimetre of distilled water at 

 a temperature of 4" C. 



1 The dyne is the force which applied to the unit of mass 

 produces a unit of acceleration. 



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