Cor. And hence if more leſſer bodies revolve about the great one, it may eaſily be inferred that the orbits deſcribed will approach nearer to ellipſes, and the deſcriptions of area's will be more nearly equable, if all the bodies mutually attract and agitate each other with accelerative forces that are as their abſolute forces directly, and the ſquares of the diſtances inverſely; and if the focus of each orbit be placed in the common centre of gravity of all the interior bodies; (that is, if the focus of gravity and innermoſt orbit be placed in the centre of gravity of the greateſt and innermoſt body; the focus of the ſecond orbit in the common centre of gravity of the two innermoſt bodies; the focus of the third orbit in the common centre of gravity of the three innermoſt; and ſo on) than if the innermoſt body were at reſt, and was made the common focus of all the orbits.
Proposition LXIX. Theorem XXIX.
In a ſyſtem of ſeveral bodies A, B, C, D, &c. if any one of thoſ bodies or A, attract all the reſt, B, C, D, &c. with accelerative forces that are reciprocally as the ſquares of the diſtances from the attracting body; the
