238 Of the SOLIDS 
THEN, if we find 9 fuch that fin g = oe x = the attrac- 
AL" AC 
tion of the rectangle CL is 7. p, n denoting the thicknefs of the 
plate. 
; _. BL |, BN ‘ vali 
So alfo, if fing =a * AN’ the attraction of LN is = 
2.Q. 
Ir fing’ = a x oer the attraction of NL’ is = 2. 9’. 
Lastriy, i ine? = = x ao the attraction of L‘'C = 
ee ie 
Tuus the whole effet of the plane MD’, or f = 
n(ote+eo+ ?”). 
WE may either fuppofe ¢, ¢ &c. defined as above, or by the 
following equations, where 7, 7', 1’, &c. denote the angles fub- 
tended by the fides of the reCtangles that meet in B, beginning 
with BC, and going round by L, N and L’ to C. 
fine = fing .finy’ 
fine’ = fin, .finy’ 
fin 9? = fin,’ . finn” 
fin Q” = fin n . fin y. 
Ir the computation is to be made by the natural fines, it will 
be better to ufe the following formule : 
fin = cof (1 —1)—Scof(n +2’) 
fing = Leof (x — xf) —2 cof Gr! +9”) 
fin 9” 
