Edmund Halley, an English astronomer, born at Haggerston, near London, Oct. 29, 1656, died at Lee, near Greenwich, Jan. 14, 1742. He was educated at Oxford. His first published essay was "A Direct and Geometrical Method of finding the Aphelia and Eccentricity of Planets" (1675). In November, 1676, he sidled for St. Helena, to form a catalogue of the fixed stars of the southern hemisphere; he returned in 1678, and the next year published his Catalog us Stellarum Australium, containing the positions of 360 stars, and numerous other observations. In 1678 he was elected a fellow of the royal society, and in 1679, at the request of that society, went to Dantzic to settle an astronomical controversy between Hooke and Hevelius. In 1681 he set out on a continental tour, and in December, when near Paris, he discovered the comet known by his name; his prediction of its return was the first of the kind that proved correct. In 1683 he published his "Theory of the Variation of the Magnetic Compass," in which he considers the earth as a vast magnet, having four magnetic poles, two near its N. and two near its S. pole, the needle always being governed by the nearest.

In the same year he was led to examine Kepler's laws of the planetary motions, and from them to infer that the centripetal force always varies inversely as the square of the distance. Visiting Newton at Cambridge, to obtain aid in proving this geometrically, he was delighted to find that the latter had perfectly demonstrated the laws of the celestial motions. He soon gave to the royal society an account of Newton's treatise De Motu, which was entered on their register; and at a later period he prevailed on the great philosopher to complete his Principia, the first volume of which was printed by Halley at his own expense. In 1686 he published an account of the trade winds and monsoons near the tropics; and among oilier valuable papers were one in 1691 on the circulation of watery vapors and the origin of springs, and another showing the importance of observing the conjunctions of the superior planets, as a means of determining the sun's parallax and distance front the earth. In the same year he was a candidate for the Savilian chair of astronomy at Oxford, but failed to obtain it mainly on account of what were regarded as his infidel opinions, though it is now said that the only ground for this charge was, that he asserted the existence of a pre-Adamite earth, out of the ruins of which our present earth was made.

In 1692 he published his modified theory of the changes in the magnetic varia-tion, and to test its correctness by observation obtained from King William the appointment of captain of a vessel, in which in two successive voyages he finished his experiments; returning home in 1700, he published his chart of the compass variations, and received the title of captain in the royal navy, with half pay for life. On the recommendation of Queen Anne, and at the request of the emperor of Germany, he went twice to the Adriatic to plan the formation of a harbor. In 1703, on the death of Dr. Wallis, he was chosen Savilian professor of geometry at Oxford. Soon after he began, with Gregory, the publication of the works of the ancient geometers; and several of their treatises, translated and edited by them, appeared in 1706-'10. In 1720, after the death of Flamsteed, he was appointed astronomer royal; and though now 64 years of age, he continued for 20 years, without an assistant, to carry on the operations of the Greenwich observatory. In 1721 he published his method of finding the longitude at sea; and in 1725 drew up his tables for computing the places of the planets, which, however, as he delayed publishing that he might perfect them, did not appear till 1749, after his death.

In 1737 he was struck with paralysis.