SIR G. GREENHILL ON ELECTROMAGNETIC INTEGRALS. 51 



12. By logarithmic differentiation of (6), 10, 



and with s = s a , s 1( for r 2 = + r a r a , 

 (2) *=! = 



(3) 



4a 





(6) ^ = (f'-r.V) 



s,}ds 2a< 



(7) 



Then with 

 (8) = 2; 



/ q \ , ac?0 2ad 



PQ 



= dn/K'd2eK = 

 Comparing this with the previous form in (4), 3, 

 (10) 



(11) 



. 

 PB ~ AP G " EB AP 



(12) (!-K) K = Gy', K-c' = 



VOL. CCXX. A. I 



