28 Prof. Maxwell on the Process of Diffusion of two or 



The equation of motion of one of the gases through the plug 

 is found by adding the forces due to pressures to those due to 

 resistances, and equating these to the moving force, which in 

 the case of slow motions may be neglected altogether. The 

 result for the first is 



Making use of the simplifications we have just discovered, this 

 becomes 



whence 



dp Kljvfyi + Vfpj . r44 x 



dx v^+v*' ' "' 



whence the rate of diffusion due to the motion of translation 

 may be found; for 



Q,= 2,andQ,--J (45) 



To find the diffusion due to the motion of agitation, we must 

 find the value of q v 



L d p x 



v Y dx 1 + KL(i?j p x -f- Vet p 2 ' 



*.=-^iO+ KL ^.+^> • ■ (46) 



Similarly, 



^ = +il (l+KLp ' ( ^ +ft) > • • (47) 



The whole diffusions are Q 1 + q x and Q*-hf* Th e values of q x 

 and q 2 have a term not following Graham's law of the square 

 roots of the specific gravities, but following the law of equal 

 volumes. The closer the material of the plug, the less will this 

 term affect the result. 



Our assumptions that the porous plug acts like a system of 

 fixed particles, and that Graham's law is fulfilled more accurately 

 the more compact the material of the plug, are scarcely suffi- 

 ciently well verified for the foundation of a theory of gases; and 



