IN THIS THIRD EDITION, supervised by Henry Pemberton, M.D., a man greatly skilled in these matters, some things in the second book concerning the resistance of mediums are explained a little more fully than previously, and new experiments are added concerning the resistance of heavy bodies falling in air. In the third book, the argument proving that the moon is kept in its orbit by gravity is presented a little more fully; and new observations, made by Mr. Pound, on the proportion of the diameters of Jupiter to each other have been added. There are also added some observations of the comet that appeared in 1680, which were made in Germany during the month of November by Mr. Kirk, and which recently came into our hands; these observations make it clear how closely parabolic orbits correspond to the motions of comets. The orbit of that comet, by Halley’s computations, is determined a little more accurately than heretofore, and in an ellipse. And it is shown that the comet traversed its course through nine signs of the heavens in this elliptical orbit just as exactly as the planets move in the elliptical orbits given by astronomy. There is also added the orbit of the comet that appeared in the year 1713, which was calculated by Mr. Bradley, professor of astronomy at Oxford.
Is. Newton
London,
12 Jan. 1725/6.
[In the third edition, the final Author’s Preface was followed by a two-page table of contents and a list of corrigenda.]