204 Mr. J. C. Maxwell on the Dynamical Theory of Gases. 



sible agitation or heat ; the second, third, and fourth represent 

 the cooling by expansion ; the fifth, sixth, and seventh the heat- 

 ing effect of fluid-friction or viscosity ; and the last the loss of 

 heat by conduction. The quantities on the other side of the 

 equation represent the thermal effects of diffusion, and the com- 

 munication of heat from one gas to the other. 



The equation may be simplified in various cases, which we 

 shall take in order. 



1st. Equilibrium of Temperature between two Gases. — Law of 

 Equivalent Volumes. 

 We shall suppose that there is no motion of translation, and 

 no transfer of heat by conduction through either gas. The 

 equation (94) is then reduced to the following form, 



-Mtff+tf+m}- ........ J 



If we put 



M V(£ 2 +% 2 +&*)=Q 1J and 



M.+M, 



(96) 



M x +M 2 

 we find 



^(Q 2 -Q 1 ) = - lii ^(M 2P2 /3 1 + M lPl /3 3 )(Q 2 -Q 1 ) ) (97) 

 or 



Q 2 -Q 1= C e -^ -J 



wtere "=^( M ^+M lPA )^. ) • < 98 > 



If, therefore, the gases are in contact and undisturbed, Q x 

 and Gl 2 will rapidly become equal. Now the state into which 

 two bodies come by exchange of invisible agitation is called 

 equilibrium of heat or equality of temperature. Hence, when 

 two gases are at the same temperature, 



Qi=Q„ ' (99) 



or 



Q 2 -M 2 (£ 2 2 +77 2 2 +r 2 2 ) 



M^ 



_ Vi 



Ei 

 El 



Up 



Pi 



