[ + 3 8 ] • 
for its tendency is to puOi the earth diredly from the 
iun. I need not fay, that it is infinitely too fmall, in 
comparifon of the fun’s attraction, to produce any 
fenfible effeCt. 
which they cover, that is, as gf x the circumference of the circle 
of which T f is the radius, that is, as gf x in the right line T f. 
But that part of the force of each particle, impinging on the 
zone p q on, which is perpendicular to the furface of the zone, is 
as of if TB (the femidiameter of the earth) be put for the whole 
force. For join 'To, and draw f K perpendicular to 'To. The 
particle impinging at o moves in the direction of Let the tight 
line of then exprefs its whole force, and this force of is com- 
pofed of the two o K, K y, of which cK is perpendicular to 
the furface of the fphcre at o, 2nd K f is parallel to it. But 
0 K : of— of-. oT or TB. Again, through K, draw Kt per- 
pendicular to of The force is refolved into two ot , tk, of 
which ot is perpendicular to the plane of the terminator, and 
is the only part of the force oK, which tends to produce 
a progreffive motion of the globe, in the direction of the 
impinging particles, that is, dire&ly from the fun. The other 
part t K urges the center of the globe along the plane of the ter- 
minator ; but the forces t K being equal and contrary on oppofite 
fides of, and at equal diftances from, the perpendicular ray, de- 
flioy each ether’s effects. Now it has been {hewn, that the whole 
force of the particle impinging at 0 is to that part of its force 
which is perpendicular to the earth’s furface at 0, as TB to of 
And it is manifeft that 0 K is to ot, that is, the perpendicular 
force, of the particle impinging at 0, is to that part of it, which is 
effective in moving the earth’s center, as TB to of. Therefore 
the whole force of the particle impinging at 0 is to its 
effective part, as TB 1 to of 1 . That is, the effe&ive part is 
as of 1 . The number of particles impinging on the zone, has 
been (hewn to be as ^/x T f. The progreffive force of motion 
excited in the earth’s c enter, by all the particles impinging on the 
infiniuflimal zon e pqon, muft be, as the number of the particles 
and the effective part of each, jointly ; that is, as gfx T/x c/' 1 > 
or writing a for TB, and x for Bf as * x a — x X lax — x 1 . And 
this is the fluxion of the progreffive force of motion excited in the 
globe, by the particles impinging upon that fegment of the 
The 
