202 r^H. Helmholtz on the Interaction of Natural Forces. 



tinue to be such ; tlie other, to Avhich a portion of the heat of 

 the warmer bodies, and the total supply of chemical, mechanical, 

 electrical, and magnetical forces belong, is capable of the most 

 varied changes of form, and constitutes the whole wealth of 

 change which takes place in natm^e. 



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 force. This is also generally the case 

 in every electrical and chemical process. From this it follows, 

 that the first portion of the store of force, the unchangeable 

 heat, is augmented by every natural j)rocess, Avhile the second 

 portion, mechanical, electrical, and chemical force, must be di- 

 minished; so that if the universe be delivered over to the un- 

 disturbed action of its physical processes, all force will finally 

 pass into the form of heat, atid all heat come into a state of 

 equilibrium. Then all possibility of a further change w^ould be 

 at an end, and the complete cessation of all natural processes 

 must set in. The life of men, animals, and plants, could not of 

 course continue if the sun had lost his high temperature, and 

 with it his light, — if all the components of the earth's surface 

 had closed those combinations which their affinities demand. 

 In short, the universe from that time forward Avould be con- 

 demned to a state of eternal rest. 



These consequences of the law of Carnot are of course only 

 valid, provided that the law, when sufficiently tested, proves to 

 be universally correct. In the mean time there is little prospect 

 of the law being proved incorrect At all events we must ad- 

 mire the sagacity of Thomson, who, in the letters of a long- 

 known little mathematical formula, which only speaks of the 

 heat, volume and pressure of the bodies, was able to discern con- 

 sequences which threatened the universe, though certainly after 

 an infinite period of time, with eternal death. 



I have already given you notice that our path lay through a 

 thorny and unrefreshing field of mathematico-mechanical devel- 

 opments. We have now left this portion of our road behind us. 

 The general principle which I have sought to lay before you has 

 conducted us to a point from which our view is a wade one, and 

 aided by this principle, we can now at pleasure regard this or 

 the other side of the surrounding world, according as our inter- 

 est in the matter leads us. A glance into the narrow laboratory 

 of the physicist, with its small appliances and complicated ab- 

 stractions, will not be so attractive as a glance at the wide heaven 

 above us, the clouds, the rivers, the woods, and the living beings 

 around us. While resrardins- the laws which have been deduced 



