38 FRAGMENTS OF SCIENCE. 



in the pursuit of this object. The faith in such a consum- 

 mation, involving as it did immense personal interest to 

 the inventor, was extremely exciting, and every attempt to 

 destroy this faith was met by bitter resentment on the 

 part of those who held it. Gradually, however, as men 

 became more and more acquainted with the true functions 

 of machinery, the dream dissolved. The hope of getting 

 work out of mere mechanical combinations disappeared; 

 but still there remained for the speculator a cloud-land 

 denser than that which filled the imagination of the Tyrol- 

 ese priest, and out of which he still hoped to evolve per- 

 petual motion. There was the mystic store of chemic 

 force, which nobody understood ; there were heat and 

 light, electricity and magnetism, all competent to produce 

 mechanical motions. 1 Here, then, is the mine in which 

 Ave must seek our gem. A modified and more refined form 

 of the ancient faith revived \ and, for aught I know, a rem- 

 nant of sanguine designers may at the present moment be 

 engaged on the problem which like-minded men in former 

 years left unsolved. 



And why should a perpetual motion, even under modern 

 conditions, be impossible ? The answer to this question is 

 the statement of that great generalization of modern sci- 

 ence, which is known under the name of the Conservation 

 of Energ} r . This principle asserts that no power can make 

 its appearance in Nature without an equivalent expenditure 

 of some other power ; that natural agents are so related to 

 each other as to be mutually convertible, but that no new 

 agency is created. Light runs into heat ; heat into elec- 

 tricity ; electricity into magnetism ; magnetism into me- 

 chanical force ; and mechanical force again into light and 

 heat. The Proteus changes, but he is e^er the same ; and 

 his changes in Nature, supposing no miracle to supervene, 

 are the expression, not of spontaneity, but oi physical neces- 



1 Sec Ilclmholtz — " Wechselwirkung der Naturkrafte." 



