D, the circular Plane which before was in Ecquilibrio, by reaſon that all its Parts being at equal Diſtances from the Centre could not preponderate anyway, will now by this adventitious Weight altering its Equilibrium, be forced to revolve round its Axis C, ſo that the Point A would deſcribe the Line A F. And ſo if we ſhould ſuppoſe the Weight E, hung at the Point B, by a String B E, it would make the Plane revolve the contrary Way from B to H. The Queſtion is then, what is the Situation and Quantity of two Weights, which having oppoſite Motions as D and E have, ſhall keep this Plane in Equilibrio as it was before. And I ſay, that if we ſuppoſe a line A B drawn parallel to the Horizon and the Weights to be ſuſpended upon that Line in ſuch ſort as that their Diſtances from the Centre C may be reciprocally proportional to their Weights, they will remain in Equilibrio.
But in order to demonʃtrate this, we muſt premiſe the following Lemma, that the
