Of GREATEST ATTRACTION. 225 
roid becomes oblong, and the attraction at the poles again di- 
minifhes. This we may fafely conclude from the law of con- 
tinuity, though the oblong f{pheroid has not been immediately 
confidered. 
XVIII. 
To find the force with which a particle of matter is attracted 
by a parallelepiped, in a direction perpendicular to any of its 
fides. 
First, let EM (Fig. 11.), be a parallelepiped, having the 
thicknefs CE indefinitely fmall, A, a particle fituated anywhere 
without it, and AB a perpendicular to thé plane CDMN. The 
attraction in the direction AB is to be determined. 
Lert the folid EM be divided into columns perpendicular to 
the plane NE, having indefinitely fmall rectangular bafes, and 
let CG be one of thofe columns. 
Ir the angle CAB, the azimuth of this column relatively to 
AB, be called z, CAD, its angle of elevation from A, e, and m’, 
the area of the little rectangle CF; then, as has been already 
cA the attraction of the column CG, in the direction AC, is 
= AG" - fine; and that fame attraction, reduced to the direction 
AB, is -. -fine.cofz. This is the element. of the attraction 
of the folid, and if we call that attraction f, f= a: fine. cof z. 
Now, if AB =a, becaufe 1: cofz:: AC: AB, AG= =< : 
fo that f = “. fin ¢ .. cof’. 
Bur 
