HERMANN VON HELMHOLTZ 283 



the numerous stories of the fable-rich America; and indeed a fable 

 it remained. 



It is not necessary to multiply examples further. You will infer 

 from those given, in what immediate connection heat, electricity, mag- 

 netism, 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, to excite 

 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 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 me- 

 chanical actions, which might be followed with a final gain of me- 

 chanical 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 combi- 

 nations which promised to furnish a perpetual motion, but the ques- 

 tion 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 im- 

 possible, 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 as- 

 sumption, might be easily and completely stated. It was found that 

 all known relations of force harmonize with the consequences of that 

 assumption, and a series of unknown relations were discovered at 



