Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/347

 Rh

Of the attractive forces of phærical bodies.

If to every point of a phærical urface there tend equal centripetal forces decreaing in the duplicate ratio of the distances from thoe points; I ay that a corpucle placed within that uperficies will not be attracted by thoe forces any way.

Let HIKL (Pl. 21. Fig. 4.) be that phærical uperficies, and P a corpucle placed within. Through P let there be drawn to this uperficies the two lines HK, IL, intercepting very mall arcs HI, KL; and becaue (by cor. 3. lem. 7.) the triangles HPI, LPK are alike, thoe arcs will be Rh