THE DYNAMICAL THEORY OP OASES. 



where u, v, and w are so chosen that they are the mean values of the com- 

 ponents of the velocity of all molecules of the same system in the immediate 

 neighbourhood of a given point. We shall also write 



p ............................... (49), 



where p, and p, are the densities of the two systems of molecules, that is, the 

 maw in unit of volume. We shall also write 



* ( 



MM .w 



Pi. Pit * *t an quantities the absolute values of which can be deduced 



from experiment. We have not as yet experimental data for determining 

 M, N, or K. 



We thus find for the rate of change of the various functions of the velocity, 



(a) 



- 2'} + fa 



..(52); 



also ^= - 



M t 



,-u,)(t>,~i 



{2Al 



.(53). 



(y) As the expressions for the variation of functions of three dimensions 

 in mixed media are complicated, and as we shall not have occasion to use 

 them, I shall give the case of a single medium, 



X 



(54). 



