ON THE DISSIPA TION OF ENERG Y. 469 



substance or character, using heat supplied at the 

 same temperature, and having the same lower 

 temperature available for the carrying away of 

 waste heat. 



Exhaustive consideration of all that is known 

 of the natural history of the properties of matter, 

 and of all conceivable methods for obtaining 

 mechanical work from natural sources of energy, 

 whether by heat engines, or electric engines, or 

 water-wheels, or windmills, or tidemills, or any 

 other conceivable kind of engine, proves to us that 

 the most perfectly designed engine can only be an 

 approach to the perfect engine ; and that the 

 irreversibility of actions connected with its working 

 is only part of a physical law of irreversibility 

 according to which there is a universal tendency 

 in nature to the dissipation of mechanical energy ; 

 and any partial restoration of mechanical energy is 

 impossible in inanimate material processes, and 

 is probable never effected by means of organised 

 matter, either endowed with vegetable life, or 

 subject to the will of an animal. 



Some mathematical details regarding cases of 



