357, 358] Maxwell's Theory of Diffusion 301 



we obtain equation (723) in the form 



<J>M*- . ...(724). 



A, p 



This equation is of the same form as the equation 



5) = 1-34- 

 P 



obtained for elastic spheres in Chapter XIV. Using Maxwell's values 



A, = 2-6595, A 2 = 1-3682 

 we find that 



O-L o 



- = 1-543. 



A! 



This numerical factor does not differ widely from the factor 1'34 pre- 

 viously found. The values for the ratio of 3) to tc/p found on p. 274, are all 

 intermediate between the two values 1'34 and 1*543, with the exception of 

 Carbon monoxide for which the value is 1'32. 



Energy. 



358. On substituting the values which have been found for S-, K, etc., we 

 find that equation (718) assumes the form 



o 9vo 3 

 ' 3y < 



Obviously the term on the left-hand side is the increase of heat-energy of 

 an element of the gas. On the right-hand side, the first term is the increase 

 of heat which ordinary physics regards as due to conduction, the second term 

 is that due to adiabatic expansion or compression, and the third term is that 

 which ordinary physics attributes to the action of viscosity, being in fact twice 

 the "dissipation function" of the viscous motion*. 



To the Kinetic Theory, however, conduction of heat, change of tempera- 

 ture resulting from adiabatic motion and " heat generated by viscosity " are 

 all equally resolved into the transfer of energy by molecules, so that to the 

 Kinetic Theory the equation just obtained expresses nothing more than the 

 conservation of this energy. 



* Cf. Lamb, Hydrodynamics, p. 518. 



