TH K OK KIT OF I |{ A N TS. 



39 



The values of D'Ji, needed in computing the perturbations of the second order 

 with respect to the masses being obtained in the same way, by the simple substitu- 

 tion of the second derivatives of the functions b,aDab, etc., for those functions 

 themselves in the expressions for 7i, it is not necessary to present the details of the 

 computation. 



After obtaining h and its derivatives, it will be found convenient to change the 

 arrangement of the terms. Hitherto we have kept in one series those in which 

 the sum of the indices are a constant. Now, we shall put together all those in which 



