[ 27 3 
IV. The accelerative forces of 
two fpherical bodies, A, B, upon 
a third C, are dire&ly as their 
mafles, and inverfely as the fquares 
of their central diftances ST, LT, 
(or of x and d) : which may be 
. ~ , F A d* 
thus expreiied, ^ X 
But the mafles, A, B, being as 
their refpedive denfities (which 
call r, m ), and the cubes of ( R , r), 
the femidiameters of the ipheres 
conjundly j if we write for - 
i , F j R 1 
its equal, we have - = - X — ? 
^ 1 <p in r 3 
d* 
X 
Let the mafs C be to B, as 
M to i j and ffj its force on B, 
/ 
' M’ 
will be <p M, or <p 
which 
gives 
M F s x . F 
— — - X and — 
f m d f 
s x 
Hmd' ^uppofing the apparent fe- 
midiameters of A and B to fub- 
tend the fame angle at the centre 
of C, and thence R to be to r, as 
x to d. 
V. But if S G, the femidiame- 
ter of A, be to the fuppofed femi- 
diameter S V, as q to i, then, 
E 2 the 
