234 
and passing to the limit 
i - aN 3 ) ds dP ses 
ap atta le 5° sin’ de’ ae 
Pp p— ov". sin'd 
Therefore < +7=7, ~ 
dd il 
Po 5 7% - SM b 
ey POrk saa Vy P—Por¥ 
7 Soe Uy if 2 2 
Therefore (see Boole, Differential Hquations, edit. I. p. 383) 
att gp tesing ‘| oso (np—e'p dg _ 7, ee spp, dp 
~ a? 0 v2 1 
. Dy 50%e sin" o Py ZI Sin’ 
i ue dopsun) ds dy (pe =e 
ae era he vn = db’ fuinkcel: Vy ‘dp ee 
Therefore if p st be considered constant for different points 
ra. T+ + CoP = Po) EN en a) — (PoP) cos $ (yD) 
0 % 
where a and 6 are constants ; 
N= i = PEP sin cos. at 3 Sie AP co $ (@— a) 
aube ON ae ing S a -(D=9P) sn gig —t 6) 
Uy 
Nee =) Gena a) nee 
P= —[N.ds=— P= PPd [16% (o— aa +Zg-dh ds 
% 
ee 3 2 A ‘ 
= “oF Pole — (@—a)*—(y —8)}, 
20, 
where ¢ is a constant. 
