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Sir I s a a c Newton’s Book I.

to G P, as D F bears to D E. But N O bears the fame propor-tion to O G, as M N bears to G P; consequently N O will bearthe same proportion to O G, as D F bears to D E. In the lastplace, the weight of the globe A bears the same proportion tothe other weight K, as D F bears to D E ; therefore N O bearsthe same proportion to 0 G, as the weight of the globe A bearsto the weight K. Whence it follows, that, when the centerof the globe A is in G, and the center of gravity of the weightK is in N, O will be the center of gravity common to boththe weights. After the fame manner, if the globe had beencaused to descend, the common center of gravity would havebeen found in this line M L. Since therefore no motion ofthe globe either way will make the common center of gravitydescend, it is manifest, from what has been said above, thatthe weights A and K counterpoize each other.

y6. I shall now consider the cafe of pendulums. A•pendulum is made by hanging a weight to a line, so that itmay swing backwards and forwards. This motion the geo-meters have very carefully considered, because it is the mostcommodious instrument of any for the exact measurement oftime.

yy. I have observed already a , that if a body hangingperpendicularly by a string, as the body A (in fig.48.) hangsby the string A B, be put so into motion, as to be made to a-fcend up the circular arch A C ; then as soon as it has arrived

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