ON THE DISSIPA TION OF EN ERG Y. 465 



which Carnot was led to his theory, and the true 

 reversibility of every motion in pure dynamics 

 have no place in the world of life. Even to think 

 of it (and on the merely dynamical hypothesis of 

 life we can think of it as understandingly as of the 

 origination of life and evolution of living beings 

 without creative power), we must imagine men, 

 with conscious knowledge of the future but with 

 no memory of the past, growing backward and 

 becoming again unborn ; and plants growing 

 downwards into the seeds from which they sprang. 

 But the real phenomena of life infinitely transcend 

 human science : and speculation regarding con- 

 sequences of their imagined reversal is utterly 

 unprofitable. Far otherwise, however, it is in 

 respect of the reversal of the motions of matter 

 uninfluenced by life, a very elementary considera- 

 tion of which leads to the full explanation of the 

 theory of the dissipation of energy. 



Carnot's theory of the perfect heat engine is 



essentially founded on the consideration of a 



reversible cycle of processes. The perfect engine 



is essentially an engine which can be worked 



VOL. II. H H 



