4 FRAGMENTS OF SCIENCE. 



true functions of machinery, the dream dissolved, 

 hope of getting work out of mere mechanical combim 

 tions disappeared: but still there remained for tl 

 speculator a cloud-land denser than that which fill* 

 the imagination of the Tyrolese priest, and out 

 which he still hoped to evolve perpetual motion, 

 was the mystic store of chemic force, which nobody 

 understood ; there were heat and light, electricity 

 magnetism, all competent to produce mechanic 

 motion. 1 Here, then, was the mine in which our 

 must be sought. A modified and more refined foi 

 of the ancient faith revived ; and, for aught I 

 a remnant of sanguine designers may at the presei 

 moment be engaged on the problem which like-mind( 

 men in former ages left unsolved. 



And why should a perpetual motion, even un( 

 modern conditions, be impossible?. The answer to this 

 question is the statement of that great generalisation 

 of modern science, which is known under the name of 

 the Conservation of Energy. This principle asserts 

 that no power can make its appearance in nature with- 

 out 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 electricity ; 

 electricity into magnetism ; magnetism into mechanical 

 force ; and mechanical force again into light and heat. 

 The Proteus changes, but he is ever the same; and 

 his changes in nature, supposing no miracle to super- 

 vene, are the expression, not of spontaneity, but of 

 physical necessity. A. perpetual motion, then, is 

 deemed impossible, because it demands the creation of 

 energy, whereas the principle of Conservation is no 

 creation, but infinite conversion. 



1 See Helmholta : Wechselwirkung der Naturkrafte.' 



