Of GREATEST ATTRACTION. 233 
BD, BM, BM’, BD’, which make up the whole rectangle DM’, 
that its attraction in the direGtion AB is expounded by the area 
of the fpherical quadrilateral fubtended by it, and, therefore, 
that the attraction of the whole rectangle MD’, is expounded by 
the fum of thefe f{pherical quadrilaterals, that is, by the whole 
quadrilateral fubtended by MD’. In the fame manner, if the 
perpendicular from the attracted particle, were to meet the 
plane without the reGtangle MD’, the difference between the 
{pherical quadrilaterals fubtended by MC and M’C, would give 
the quadrilateral, fubtended by the rectangle MD’, for the va- 
lue of the attraction of that rectangle. 
‘ THEREFORE, i in general, if a particle’ A, gravitate to a rec- 
tangular.plane, or to a solid indefinitely thin, contained between. 
two parallel rectangular planes, its gravitation, in the line per- 
pendicular to those planes, will be equal to the thickness of the 
solid, ‘multiplied into the avea of thespherical quadrilateral sub- 
tended by either of those planes at the centre A. 
Tue fame’ may be extended. to all planes, by/whatever figure 
they be bounded, as they may all be refolved into rectangles of 
indefinitely ‘fimiall breadth,’ and hier vee nae ie ceri i to! 
a ftraight line givenbin pofition. ' 
oTHe: gravitation’ ‘ofa point toward any’ yrphslee 2 in'a fine: per- 
pendicular tovit; is, therefore, equal-to n, a quantity that ex- 
preffes the-inténfity of ‘the attraction, multiplied into the area 
of the ‘fpherical! figure, . ory as “it” a be called, the’ angular 
{pace fubtendedvby: ‘the givensplane: I 
Tuus, in the cafe of a triangular pli eae Ais angles 
fubtended at A, by the fides of the triangle, are a, } and c; 
fince Evter has demonftrated * that the area of the fpherical 
triangle contained by thefe arches, is equal to the re@tangle un- 
Pe: der 
Q -qerzt t i t 
* Nov. Ada Petrop, 1792, p. 47. 
