41 G 
MR. W . D. NIVEN ON CERTAIN DEFINITE INTEGRALS. 
If b be small and if A — a=c be also small, then approximately 
and M becomes 
i i A 2 +c 2 
p— l + V ~JT and ( i= l ~ 
4 77 A I log 8 a / ■——- 21 
L & V tf + d 
This result is given by Clerk Maxwell. 
§ 29. If the circle of radius a be outside the sphere of radius A passing through the 
larger circuit, the value of M is 
4 a A 
"" f n COS </> COS -vp 
0 Jo^+i(A cos <f) + a cos \jr) 
d < t > cl\fj 
(g) 
The forms (e) and (g) obtained for M are interesting from their simplicity, and would 
seem to be useful in calculations connected with induction coils. 
