13 variation from the different force of grae vity of the Moon and Earth to the Sun, ariſing from different diſtances of the Moon in its ſeveral ai'pe6l:s. The mean gravity of the Moon to the Sun, he ſuppoſes, is ſatiſfied by the annual motion of the ¢Moon round the Sun; the gravity of the Moon to the Earth, he ſuppoſes, is ſatiſfied by a ref volution of the Moon about the Earth. But the difference of the Moon's gravity to the Sun more or leii; than the Earth's gravity, he ſuppoſeé, produces two effects; for as this difference of force may be reſolved into two forces, one acting in the Way, or contrary to the Way, of the Moon about the Earth, and the other acting in 'the line to or from the Earth: the firſt: cauſes the Moon to deſcribe .a larger or ſmaller area in the ſame time about the Earth, according as it tends to accelerate or retard it; the other changes the form of the lunar orbit from what' it ought to be merely from the Moonfs gravity to the Earth, and both together make up that inequality which is called the variation. But ſince the real motion of the Moon, Ii1D'a Iimaile motion, cauſed by a congnual dew élzion from a itreight line, by H the l
