166 ON THE INTERACTION OF NATURAL FORCES. 



Starting from each of these different manifestations of 

 natural forces, we can set every other in motion, for the 

 most part not in one way merely, but in many ways. It 

 is here as with the weaver's web, 



Where a step stirs a thousand threads, 



The shuttles shoot from side to side, 



The fibres flow unseen, 



And one shock strikes a thousand combinations. 



Now it is clear that if by any means we could succeed, 

 as the above American professed to have done, by me- 

 chanical forces, in exciting chemical, electrical, or other 

 natural processes, which, by any circuit whatever, and 

 without altering permanently the active masses in the 

 machine, could produce mechanical force in greater quan- 

 tity than that at first applied, a portion of the work thus 

 gained might be made use of to keep the machine in 

 motion, while the rest of the work might be applied to 

 any other purpose whatever. The problem was to find, 

 in the complicated net of reciprocal actions, a track 

 through chemical, electrical, magnetical, and thermic 

 processes, back to mechanical actions, which might be 

 followed with a final gain of mechanical work : thus would 

 the perpetual motion be found. 



But, warned by the futility of former experiments, the 

 public had become wiser. On the whole, people did not 

 seek much after combinations which promised to furnish 

 a perpetual motion, but the question was inverted. It 

 was no more asked, How can I make use of the known 

 and unknown relations of natural forces so as to construct 

 a perpetual motion? but it was asked, If a perpetual 

 motion be impossible, what are the relations which must 

 subsist between natural forces ? Everything was gained 

 by this inversion of the question. The relations of natural 

 forces rendered necessary by the above assumption, might 



