24 



THE ANIMAL AS A MACHINE. 



machinery properly operated ; and hence the important 

 principle : 



In engineering, the principles of pure mechanism, of 

 theoretical mechanics, and pure theory in the science 

 of energetics, or of thermodynamics, are to be studied 

 as introductory to a science of appHcation in which all 

 actions and all calculations are to be considered with 

 reference to the modifications produced by the wastes 

 of energy and the alteration of the magnitudes and 

 other properties of forces consequent upon the occur- 

 rence of friction. 



7. The Laws of Energetics, the basis of the science 

 which it has been proposed to call by that name, are : 



(1) T'he Law of Persistence, or of Conservation of 

 Energy: — Existing energy can never be annihilated; 

 and the total energy, actual and potential, of any iso- 

 lated system can never change. 



This is evidently a corollary of that grander law, 

 asserting the indestructibiHty of all the work of creation, 

 which has already been enunciated. 



(2) The Law of Dissipation, or of Degradation of 

 Energy : — All energy tends to diffuse itself through- 

 out space, with a continual loss of intensity, with what 

 seems, now, to be the inevitable result of complete and 

 uniform dispersion throughout the universe, and, con- 

 sequently, entire loss of availability. 



It is only by differences in the intensity of energy, 

 and the consequent tendency to forcible dispersion, 

 that it is possible to make it available in the production 

 of work. 



(3) The Law of Transformation of Energy : — Energy 

 may be transformed from one condition to another, 

 or from any one kind or state to any other ; changing 



