IN UAKIFIED GASES 



.(24) 



which giro the condition 



a 4.0 + y = (25). 



Let m nt find the mean value of ( in the same way, denoting the result 

 by the symbol 



Since in what follows we shall denote the velocity-components of each 

 molecule by v + f, v+q, to+{, where u, v, w are the velocity-components of 

 the centre of mass of all the molecules within the element, it follows that the 

 values of 17, C are each of them zero. We thus obtain the equations 



.(27). 



Remembering these conditions, we find that the mean values of combina- 

 tions of two, three, and four dimensions are of the forms 



= 7?0(l + a')l 



.(28) 



.(29) 



2a') 



.(30). 



(5) Rates of Decay of these Mean Values. 



If any term of Q in equation (20) contains symbols belonging to one 

 group alone of the molecules, the corresponding term of the integral may be 

 f-und from the above table, but if it contains symbols belonging to both 



