[ 76 -] 
T A B.' IV^. 
. FIG. I. 
Proposition. 
I F a body (P), projeded in a given diredion, bo 
conftantly drawn towards two fixed points (S andT), 
which are not both in the fame plane with the di- 
redion, the triangle (SPT), formed by right lines 
drawn from the body (P) to thofe fixed points 
(S andT), flialldefcribe equal folids (STPP\STP'P"), 
in equal times, about the right line (ST) joining the 
faid points. 
Fig. 2. For, fuppofe a body projeded in the 
diredion PP\ and aded upon by two centripetal forces 
towards the fixed points S and T j the angles PT S, 
PTT lying in different planes. Let the time be di- 
vided into equal moments. 
In the firft moment, fuppofe the body, . by its 
given force, fhould move along the line P P'i and in 
the fecond moment, if no new force was added, it 
fhould continue to move in the fame right line along 
P'^— PPh but when the body has come to P\ fup- 
pofe it aded upon by the two centripetal forces, in the 
diredions P'T, P^S ; and let thofe forces be in pro- 
portion to that in the diredion PP\ as the lines PV, 
Vs to the line P> (r^PT). 
With thefe three right lines P'y>, PV, PV, complete 
the parallelopipid PT'^ i and the body in P\ being 
aded upon by thefe three forces, in the diredions 
p>. 
