SYSTEMS COMPOSED OF MOLECULES. 199 



Equation (505), which we repeat in a slightly different 

 form, viz., 



phases 



shows that O is a function of and p v . . . fj, h ; also of the 

 external coordinates 1? a 2 , etc., which are involved implicitly 

 in e. If we differentiate the equation regarding all these 

 quantities as variable, we have 



la 



phases 



phases 



+ etc. 



all 



de e 



phases 



- etc. (523) 



5 



If we multiply this equation by e 9 , and set as usual A v A v 

 etc., for de/da^ delda^, etc., we get in virtue of the law 

 expressed by equation (519), 



dto O _ d - 



