ME. CLERK MAXWELL OX THE DYNAMICAL THEORY OF GASES. 
i i 
and eliminating by means of equations (76) and (52), we find 
+**f. (£+$) +*«■ (£+2) +i.e* (I +5) | 
In this equation the first term represents the variation of invisible agitation or heat ; 
the second, third, and fourth represent the cooling by expansion ; the fifth, sixth, and 
seventh the heating 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 communication of heat from one gas to the other. 
The equation may be simplified in various cases, which we shall take in order. 
( 94 ] 
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, 
If we put 
we find 
m“ 1 M.«+^+R)=Q» and + +rt+ £) = Q» • • • • 
|-(Q a _Q 1 )=_^^(M 2f2 /3 1 +M jfl ^)(Q 2 -Q 1 ), 
Q 2 —Qj.=Ce~ nt , where ^^(M^+M,^.)!-. . 
(95) 
(96) 
(97) 
(98) 
If, therefore, the gases are in contact and undisturbed, Q, and Q 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, 
Q,=Q* 
2 Q, + 
M,^l 
£i. 
mJ— 
or 
(99) 
