148 ON THE INTERACTION OF NATURAL FORCES. 



It is not necessary to multiply examples further. You will 

 infer from those given in what immediate connection heat, 

 electricity, magnetism, light, and chemical affinity, stand with 

 mechanical 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 mechanical 

 forces, in exciting chemical, electrical, or other natural pro- 

 cesses, which, by any circuit whatever, and without altering 

 permanently the active masses in the machine, could produce 

 mechanical force in greater quantity 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 rela- 

 tions 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, 



