4*4 POPULAR LECTURES AND ADDRESSES. 



9 

 a case of affirmative answer for Carnot's last 



thermodynamic question. The influence of animal 

 or vegetable life on matter 1 is infinitely beyond 

 the range of any scientific inquiry hitherto entered 

 on. Its power of directing the motions of moving 

 particles, in the demonstrated daily miracle of our 

 human free-will, and in the growth of generation 

 after generation of plants from a single seed, arc 

 infinitely different from any possible result of the 

 fortuitous concourse of atoms ; and the fortuitous 

 concourse of atoms is tJie sole foundation in Phi- 

 losophy on which can be founded the doctrine that 

 it is impossible to derive mechanical effect from heat 

 otlicrwise than by taking heat from a body at a 

 higher temperature, converting at most a definite, 

 proportion of it into median ical effect, and giving 

 out the whole residue to matter at a lower 

 temperature. 



The considerations of ideal reversibility, by 



1 About twenty-five years ago, 1 asked Liebig if he believed that a 



leaf or a flower could be formed or could grow by chemical forces. 



:iswered, " I would more readily believe that a book on 



chemistry or on botany could grow out of dead matter by chemical 



