ON THE AGE OF THE SUN'S HEAT. 



^Reprinted by permission from "Macmillan's Magazine" 

 March, 1862.] 



THE second great law of Thermodynamics 

 involves a certain principle of irreversible action 

 in nature. It is thus shown that, although 

 mechanical energy is indestructible, there is a 

 universal tendency to its dissipation, which 

 produces gradual augmentation and diffusion of 

 heat, cessation of motion, and exhaustion of 

 potential energy through the material universe. 1 

 The result would inevitably be a state of universal 

 rest and death, if the universe were finite and left 

 to obey existing laws. But it is impossible to 

 conceive a limit to the extent of matter in the 



1 See "On a Universal Tendency in Nature to the Dissipation 

 of Mechanical Energy," Proceedings of the Royal Society of 

 Edinburgh, April 19, 1852 ; or the Philosophical Magazine, 

 October, 1852 ; also Mathematical and Physical Papers, Vol. I. 

 Article LIX. 



