THE SORTING DEMON OF MAXWELL 141 



translational motions. The motivity (or energy 

 for motive power) in the explosive mixture of 

 oxygen and hydrogen of the one case, and the 

 separated mutual combustibles, carbon and oxygen, 

 of the other case, thus obtained, is a transforma- 

 tion of the energy found in the substance in the 

 form of kinetic energy of the thermal motions of 

 the compound molecules. Essentially different 

 is the decomposition of carbonic acid and water 

 in the natural growth of plants, the resulting 

 motivity of which is taken from the undulations 

 of light or radiant heat> emanating from the 

 intensely hot matter of the sun. 



The conception of the " sorting demon " is 

 merely mechanical, and is of great value in purely 

 physical science. It was not invented to help us 

 to deal with questions regarding the influence of 

 life and of mind on the motions of matter, 

 questions essentially beyond the range of mere 

 dynamics. 



The discourse was illustrated by a series of 

 experiments. 



