Prof. Helmholtz oti the Interaction of Natural Forces. 491 



A connexion between the taking-in of nourishment and the de- 

 velopment of force did not make itself apparent. The nourish- 

 ment seemed only necessary to grease^ as it were, the wheelwork 

 of the animal machine, to replace what was used up, and to renew 

 the old. The development of force out of itself seemed to be 

 the essential jieculiarity, the real quintessence of organic life. 

 If, therefore, men were to be constructed, a perpetual motion 

 must first be found. 



Another hope also seemed to take up incidentally the second 

 place, which in our wiser age would certainly have claimed 

 the first rank in the thoughts of men. The perpetual motion 

 was to produce work inexhaustibly without corresponding con- 

 sumption, that is to say, out of nothing. Work, however, is 

 money. Here, therefore, the great practical problem which the 

 cunning heads of all centuries have followed in the most diverse 

 ways, namely to fabricate money out of nothing, invited solution. 

 The similarity with the philosopher's stone sought by the ancient 

 chemists was complete. That also was thought to contain the 

 quintessence of organic life, and to be capable of producing gold. 



The spur which drove men to inquiry was sharp, and the talent 

 of some of the seekers must not be estimated as small. The 

 nature of the problem was quite calculated to entice poi'ing 

 brains, to lead them round a circle for years, deceiving ever with 

 new expectations which vanished upon nearer approach, andfinally 

 reducing these dupes of hope to open insanity. The phantom 

 could not be grasped. It would be impossible to give a history 

 of these efibrts, as the clearer heads, among whom the elder Droz 

 must be ranked, convinced themselves of the futility of their ex- 

 periments, and were naturally not inclined to speak much about 

 them. Bewildered intellects, however, proclaimed often enough 

 that they had discovered the grand secret ; and as the incorrect- 

 ness of their proceedings was always speedily manifest, the matter 

 fell into bad repute, and the opinion strengthened itself more 

 and more that the problem was not capable of solution ; one diffi- 

 culty after another was bi'ought under the dominion of mathe- 

 matical mechanics, and finally a point was reached where it could 

 be proved, that at least by the use of pure mechanical forces no 

 perpetual motion could be generated. 



We have here arrived at the idea of the driving force or 

 power of a machine, and shall have much to do with it in 

 future. I must therefore give an explanation of it. The idea of 

 work is evidently transferred to machines by comparing their 

 arrangements with those of men and animals, to replace which 

 they were applied. We still reckon the work of steam-engines 

 according to horse power. The value of manual labour is deter- 

 mined partly by the force which is expended in it (a strong 

 2K2 



