THE BIRTH AND DEATH OF WORLDS 415 



dynamics, that produced the steam-engine, the marvellous con- 

 trivances of Vaucanson, of Droz, and many another. 



This wonderful advance inspired astonishing dreams. In- 

 ventive geniuses, some of them of the highest order, laboured 

 to produce mechanisms which should imitate and do the work 

 of man. Some of them succeeded so well that they were haled 

 before the Inquisition not merely the makers, but the 

 mechanisms as products of the black art. A vaster and 

 wilder dream was that of perpetual motion, some device which 

 should give out more power than it consumed, some contri- 

 vance by which the work of the world might be largely lifted 

 from human shoulders. It seems fantastic to us now ; through- 

 out a long period it was the constant preoccupation of many 

 sane and resourceful minds. The prevailing ideas of force 

 were vague ; of the present-day conceptions there were but 

 adumbrations. Jt seemed reserved for the nineteenth century 

 to clarify these ideas and to set the limits of mechanical 

 possibility. 



The foundations were laid by an American. In the years 

 that immediately followed the close of the Colonial Rebellion, 

 a refugee from the revolted colonies, Benjamin Thompson 

 (created Count Rumford) had instituted a remarkable series 

 of experiments upon the nature of heat. Laplace and Lavoisier 

 the chemist had jointly made an important contribution. Some 

 time after, another Frenchman, a young engineer named Carnot, 

 laid the foundation of the modern science of thermo-dynamics 

 that is to say, of the energy of heat. It appeared in a brief 

 but very remarkable memoir, no sooner printed than straight 

 away forgotten. 



It was not until the early forties of the last century that 

 this solution of ideas, as it were, crystallised out. This came 

 in the expression of a law something akin to that which Lavoisier 

 had established as to the indestructibility of matter the in- 

 destructibility of energy in Spencerian phrase, the persistence 

 of force. It embodied the idea that the powers of nature, the 

 forces of heat, of light, of electricity broadly, the ability to 

 perform work represented a sum total of potential in the 

 universe which remained unchanged. These forces may be 

 converted one into the other : from light may come heat ; 

 from heat may come the energy of steam ; from steam may 

 come the motive-power to drive mills or dynamos. These 



