ſquares of the diſtances from that great body; eſpecially if the inequality of this proportion be greater than the inequality of the proportion of the diſtances from the great body. For if the accelerative force, acting in parallel directions and equally, cauſes no perturbation in the motions of the parts of the ſyſtem, it muſt of courſe, when it acts unequally, cauſe a perturbation ſomewhere, which will be greater or leſs as the inequality is greater or leſs. The exceſs of the greater impulſes acting upon ſome bodies, and not acting upon others, muſt neceſſarily change their ſituation among themſelves. And this perturbation, added to the perturbation ariſing from the inequality and inclination of the lines, makes the whole perturbation greater.
Cor. 3. Hence if the parts of this ſyſtem move in ellipſes or circles without any remarkable perturbation; it is manifeſt, that if they are at all impelled by accelerative forces tending to any other bodies, the impulſe is very weak, or elſe is impreſſed very near equally and in parallel directions upon all of them,
Proposition LXVI. Theorem XXVI.
If three bodies whoſe forces decreaſe in a duplicate ratio of the diſtances, attract each other mutually; and the accelerative attractions of any two towards the third be between themſelves reciprocally as the ſquares of the diſtances and the two leaſs revolve
