6 ART. 15. — H. NAGAOKA: NOTE ON THE POTENTIAL 



This expression coincides witli that obtained in the usual 

 manner from F. Neumann's formula. 



§ 5. Evaluation of f or solid amjlc subtended by a circle. — Denot- 

 ing the integral entering- in (/!') by ii, we have 



(a — X cos 6) dd 



B: 



ax 



or + x' + z- 

 ax 



we easily find 



sin d^d^ + x^ + -2"' — 2 ax cos d=^4:{s — e^) (s — e.J (s — e^) 



where 



whence 



= V4 s^—g-iS-g^^^/ S 



2B V-B a + B) 



1 3F-^-l 1 , _ 2J3(F^-{) 



^=1 T^r r 



Ä'=- '^ ^""^ 



l-l-8i3 (a + a;)- + .r 

 3J3 + 1 {a-^xj^f 



(8) 



r, r, r (a — x COS u) ao 



2J=:2 azl ., .> r. a 



J (d--\-x^—2ax COS 0) ^d- + x'+z^— 2aa; cos a 

 



Puttinsf cosd=As + B, where 



A = l^)K (9) 



\ ax / 



(10) 



(11) 



