THE FOKCES OF NATURE DISSIPATED IN HEAT. 229 



the unchangeable heat, is augmented by every natural pro- 

 cess, while the second portion, mechanical, electrical, and 

 chemical force, must be diminished ; so that if the universe 

 be delivered over to the undisturbed action of its physical pro- 

 cesses, all force will finally pass into the form of heat, and all 

 heat come into a state of equilibrium. Then all possibility of 

 a further change would be at an end, and the complete cessa- 

 tion of all natural processes must set in. The life of men, 

 animals, and plants, could not of course continue if the sun 

 had lost its high temperature, and with it his light, if all the 

 components of the earth's surface had closed thos.e combina- 

 tions which their affinities demand. In short, the universe 

 from that time forward would be condemned 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 admire 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 bodies, 

 was able to discern consequences which threatened the uni- 

 verse, 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 

 developments. 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 wide one, and, aided by this principle, we can now at 

 pleasure regard this or the other side of the surrounding 

 world, according as our interest in the matter leads us. A 

 glance into the narrow laboratory of the physicist, with its 

 small appliances and complicated abstractions, will not be so 

 attractive as a glance at the wide heaven above us, the clouds, 



