470 POPULAR LECTURES AND ADDRESSES. 



this law will be found in a short paper 1 in the 

 Proceedings of the Royal Society of Edinburgh for 

 April 19, 1852. The dynamical explanation of 

 it, founded essentially on consideration of the 

 vastness of the numbers of freely moving atoms 

 or particles in even the smallest portion of palpable 

 matter, and the infinity of such motions in the 

 material universe, is given in a paper entitled " The 

 Kinetic Theory of the Dissipation of Energy," 

 which was communicated to the Royal Society of 

 Edinburgh, twenty-two years later, 2 and which is 

 republished in the Philosophical Magazine for the 

 present month (March, 1892). 



We have been considering a fly-wheel or clock- 

 work driven by a weight and the heat generated by 

 friction against the motion of wheels and pendulum, 

 and by impacts of teeth against the pallets of an 

 escapement. Our knowledge of properties of 

 matter and of modes of propagation of heat by 



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

 Mechanical Energy," republished in vol. i. of Mathematical and 

 Physical Papers, pp. 511 514. 



2 Proceedings of the Royal Society of Edinburgh February 16, 

 1874. 



