unite there, and be formed into a globe. And therefore if the common centre of gravity of the attracting bodies be either at reſt, or proceeds uniformly in a right line; the attracted body will move in an ellipſis having its centre in the common centre of gravity of the attracting bodies.
Proposition XC. Problem XLIV.
If to the ſeveral points of any circle there tend equal centripetal forces, increaſing or decreaſing in any ratio of the diſtances; it is required to find the force with which a corpuſcle it attracted, that is ſituate any where in a right line which ſtands at right angles to the plane of the circle at its centre.
Suppoſe a circle to be deſcribed about the centre A (Pl. 24. Fig. 1.) with any interval AD in a plane to which the right line AP is perpendicular; and let it be required to find the force with which a corpuſcle P is attracted towards the ſame. From any point E of the circle, to the attracted corpuſcle P, let there be drawn the right line PE. In the right line PA take PF equal to PE, and make a perpendicular FK, erected at F, to be as the force with which the point E attracts the corpuſcle P. And let the curve line IKL
