to the times, and an orbit more approaching to the form of an ellipſis having its focus in that centre, than it can deſcribe round the innermoſt and greateſt body T by radii drawn to that body.
For the attractions of the bodies S (Pl. 21. Fig. 3.) towards T and P compoſe its abſolute attraction. which is more directed towards O the common centre of gravity of the bodies T and P, than it is to the greateſt body T; and which is more in a reciprocal proportion to the ſquare of the diſtance SO, than it is to the ſquare of the diſtance ST; as will eaſily appear by a little conſideration.
Proposition LXVIII. Theorem XXVIII.
The ſame laws of attraction ſuppoſed, I ſay that the exterior body S will, by radii drawn to O the common centre of gravity of the interior bodies P and T, deſcbribe round that centre, area's more proportional to the times, and an orbit more approaching to the form of an ellipſis having its focus in that centre, if the innermoſt and greateſt body be agitated by theſe attractions as well as the reſt, than it would do if that body were either
