Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 2.djvu/525

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angle of the diſtances from the foci. But in orbits like thoſe of the planets, the rules as they are delivered above are ſufficient of themſelves without further correction.

===o===

POSTSCRIPT UPON reviewing theſe few ſheets after they were printed off, which happened a little ſooner than I expected, I fear the apology I have offered for delivering the propoſitions relating to the Moon's motion, in this rude manner, without giving any proof of them, or ſo much as mentioning the fundamental principles of their demonſtration, will ſcarcely paſs as a ſatisfactory one ; eſpecially ſince there are among theſe propoſitions, ſome which, I am apt to think, cannot eaſily be proved to be either true or falſe, by any methods which are now in common uſe. WHEREFORE to render ſome ſatisfaction in this article, I ſhall add a few words concerning the principles from whence theſe propoſitions, and others of the like nature