Page:A Treatise of the Mechanical Powers - Motte - 1733.djvu/70

 D, the circular Plane which before was in Ecquilibrio, by reaon that all its Parts being at equal Ditances from the Centre could not preponderate anyway, will now by this adventitious Weight altering its Equilibrium, be forced to revolve round its Axis C, o that the Point A would decribe the Line A F. And o if we hould uppoe 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 Quetion is then, what is the Situation and Quantity of two Weights, which having oppoite Motions as D and E have, hall keep this Plane in Equilibrio as it was before. And I ay, that if we uppoe a line A B drawn parallel to the Horizon and the Weights to be upended upon that Line in uch ort as that their Ditances from the Centre C may be reciprocally proportional to their Weights, they will remain in Equilibrio.

But in order to demonʃtrate this, we mut premie the following Lemma, that the