Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/403

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Of the motion of very mall bodies when agitated by centripetal forces tending to the everal parts of any very great bofy.

If two imilar mediums be eparated from each other by a pace terminated on both ides by parallel planes, and a body in its page through that pace be attracted or impelled perpendicular towards either of tho mediums, and not agitated or hindered by any other force; and the attraction be every where the ame at equal diameter from either plane, taken towards the ame hand of the plane; I ay that the fine of incidence upon either plane will be to the due of emergence from the other plane, in a given ratio.

Let Aa and Bb (Pl. 25. Fig. 1.) be two parallel planes, and let the body light upon