HERMANN VON HELMHOLTZ 287 



the living force of the moving wind, as his possession. These por- 

 tions of the store of Nature are what give his property its chief value. 



Further, from the fact that no portion of force can be absolutely 

 lost, it does not follow that a portion may not be inapplicable to human 

 purposes. In this respect the inferences drawn by William Thomson 

 from the law of Carnot are of importance. This law, which was dis- 

 covered by Carnot during his endeavours to ascertain the relations be- 

 tween heat and mechanical force, which, however, by no means belongs 

 to the necessary consequences of the conservation of force, and which 

 Clausius was the first to modify in such a manner that it no longer 

 contradicted the above general law, expresses a certain relation be- 

 tween the compressibility, the capacity for heat, and the expansion by 

 heat of all bodies. It is not yet considered as actually proved, but 

 some remarkable deductions having been drawn from it, and after- 

 wards proved to be facts by experiment, it has attained thereby a 

 great degree of probability. Besides the mathematical form in which 

 the law was first expressed by Carnot, we can give it the following 

 more general expression: — "Only, when heat passes from a warmer 

 to a colder body, and even then only partially, can it be converted 

 into mechanical work." 



The heat of a body which we cannot cool further, cannot be changed 

 into another form of force; into the electric or chemical force, for 

 example. Thus, in our steam engines, we convert a portion of the 

 heat of the glowing coal into work, by permitting it to pass to the 

 less warm water of the boiler. If, however, all the bodies in nature 

 had the same temperature, it would be impossible to convert any 

 portion of their heat into mechanical work. According to this, we 

 can divide the total force store of the universe into two parts, one 

 of which is heat, and must continue to be such; the other, to which 

 a portion of the heat of the warmer bodies, and the total supply of 

 chemical, mechanical, electrical, and magnetical forces belong, is capa- 

 ble of the most varied changes of form, and constitutes the whole 

 wealth of change which takes place in nature. 



But the heat of the warmer bodies strives perpetually to pass to 

 bodies less warm by radiation and conduction, and thus to establish 

 an equilibrium of temperature. At each motion of a terrestrial body, 

 a portion of mechanical force passes by friction or collision into heat, 

 of which only a part can be converted back again into mechanical 



