﻿and on the Gravity-Potential of a Ring. 467 



and 



A- \{ g-|(nQi-PoQ!!) + ^° } • 



So also, in a similar manner, T n F;— T' w F n gives 



A _64i/2Ia J 



{s(Q'f-Q»Q:;)+(^|s} 



9th' 2 

 64 i/ 21 a 3 



with 



The energy is 



The part of E depending on /is found by an easy integra- 

 tion to be , -072,0 



49rRIy3 2 \ 

 3— (^j + cosec 2 «J. 



The part depending on the infinite series is 



- — -SB 1 I * dudv. 



Jo (< 



But from (9) 



' cos in; _4\/2 



_4^2i d ( q A 



3 Sc^UT/ 

 Therefore the above 



4\/2la 2 



Noi 

 also 



j¥*-J*(-«*(*4K)* 



2S + 2V 4JS" 



