Excerpt from Memoir on the Secular Variations of the Elements of the Orbits of the Eight Principal Planets, Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, and Neptune: With Tables of the Same; Together With the Obliquity of the Ecliptic, and the Precession of the Equinoxes in Both Longitude and Right Ascension The reciprocal gravitation of matter produces disturbances in the motions of the heavenly bodies, causing them to deviate from the elliptic paths which they would follow, if they were attracted only by the sun. The determination of the amount by which the actual place of a planet deviates from its true elliptic place at any time is called the problem of planetary perturbation. The analytical solution of this problem has disclosed to mathematicians the fact that the inequalities in the motions of the heavenly bodies are produced in two distinct ways. The first is a direct disturbance in the elliptic motion of the body; and the second is produced by reason of a variation of the elements of its elliptic motion. The elements of the elliptic motion of a planet are six in number, viz: the mean motion of the planet and its mean distance from the sun, the eccentricity and inclination of its orbit, and the longitude of the node and perihelion. The first two are invariable Degrees the other four are subject to both periodic and secular variations. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.