Place of greatejl Attraction. 7 
practical experiment, to fuppofe the hill to be a long 
triangular prifm, fo that all its meridional fedlions may- 
be fimilar triangles. Let therefore the triangle abc re- 
prefent its fedlion by a verti- 
cal plane palling through the 
meridian, or one lide of an 
indefinitely thin cuneuswhofe 
edge is in pg ; or rather 
pbcgp the fide of one cuneus, 
and pag the fide of another, their common edge 
being the line pg perpendicular to the bafe ac; p being 
the required point in the fide ab where the attrac- 
tion of the fedlion abc, or indefinitely thin cuneus, 
lhall be greateft in a diredlion parallel to the horizon 
ac. And then from the foregoing fuppofitions, it is 
evident that in whatever point of ab the attradlion of 
abc is greateft, there alfo will the attradlion of the 
whole hill be the greateft. 
8. Now draw hpdef parallel to ac ; and ah, pg, bi, 
cf, perpendicular to the fame. Then it is evident that 
at the point p, in the diredlion pf, the attradlion of 
pbcgp is affirmative, and that of pag negative. But 
PBCGP is = PBD + BDE + PFCG - EFC ; and PAG = PH AG - 
pha. Therefore the attradlions of pbd, bde,, pfcg, 
3? ha,, are affirmative ; and thofe of efc, phag, negative. 
Put 
