HALLEY, Dr Edmund, an eminent astronomer, was the only son of a soap-boiler in London, and was born in 1656. He first applied himself to the study of the languages and sciences, but at length gave himself up wholly to that of astronomy. In 1676 he went to the island of St Helena to complete the catalogue of fixed stars, by the addition of those situated near the south pole; and having delineated a planisphere, in which he laid them all down in their exact places, he returned to England in 1678. In the year 1680 he performed what is called the grand tour, accompanied by his friend Mr Nelson. About halfway between Calais and Paris, Halley obtained a sight of a remarkable comet, as it then appeared a second time that year, in its return from the sun. In the preceding November he bad seen it in its descent; and now hastened to complete his observations by viewing it from the royal observatory of France. His design in this part of his tour was to establish a friendly correspondence between the two astronomers royal of Greenwich and Paris, and in the mean time to improve himself under so great a master as Cassini. From France he proceeded to Italy, where he spent the greater part of the year 1681, and then returned to England. In 1683 he published his Theory of the Variation of the Magnetical Compass, in which he supposes the whole globe of the earth to be a great magnet, with four magnetical poles or points of attraction; but afterwards [7:11:120]conceiving that this theory was liable to great exceptions, he caused an application to be made to King William, who appointed him commander of the Paramour, with orders to seek by observations the discovery of the rule of variations, and to lay down the longitudes and latitudes of his majesty’s settlements in America. He set out on this attempt on the 24th of November 1698; but on crossing the line his men grew sickly, and his lieutenant having mutinied, he returned home in June 1699. Having got the lieutenant tried and cashiered, he set sail a second time in September following, with the same ship, and another of less size, of which he had also the command. He now traversed the Atlantic Ocean from one hemisphere to the other; and having made his observations at St Helena, Brazil, Cape Verd, Barbadoes, Madeira, the Canaries, the coast of Barbary, and in many other latitudes, he returned in September 1700, and the next year published a general chart, showing at one view the variation of the compass in all those places. Captain Halley, as he was now called, had been at home little more than half a year, when he was sent by the king to observe the course of the tides, with the longitude and latitude of the principal headlands in the British Channel; and having executed this task with his usual expedition and accuracy, he published a large map of the British Channel. Soon afterwards the emperor of Germany having resolved to construct a harbour for shipping in the Adriatic, Captain Halley was sent by Queen Anne to survey the different ports on the coast of Dalmatia. He embarked on the 22d of November 1702, passed over to Holland, and travelling through Germany to Vienna, proceeded to Istria; but as the Dutch opposed the design, it was laid aside. The emperor, however, made him a present of a rich diamond ring from his finger, and honoured him with a letter of recommendation, written with his own hand, to Queen Anne. Soon after his return he was again dispatched on the same business. Upon his arrival at Vienna he was the same evening presented to the emperor, who sent his chief engineer to attend him to Istria, where they repaired and added new fortifications to those of Trieste. Mr Halley returned to England in 1703; and the same year he was appointed professor of geometry in the university of Oxford, in the ’ room of Dr Wallis, and had the degree of doctor of laws conferred on him by that university. He is said to have lost the professorship of astronomy in that university because he would not profess his belief of the Christian religion. He was scarcely settled at Oxford, when he began to translate into Latin from the Arabic, Apollonius de Sectione Rationis, and to restore the two books of the same author, De Sectione Spatii, which are lost, from the account given of them by Pappus; and he published the whole in 1706. He had afterwards a share in preparing for the press the Conics of Apollonius, and he ventured to supply the whole of the eighth book, the original of which is also lost. He likewise added Serenus on the section of the cylinder and cone, printed from the original Greek, with a Latin translation, and published the whole in folio. In 1713 he was made secretary of the Royal Society; in 1720 he was appointed the king’s astronomer at the royal observatory at Greenwich, in the room of Mr Flamsteed; and in 1729 he was chosen as foreign member of the Academy of Sciences at Paris. He died at Greenwich in 1742. His principal works are, 1. Catalogus Stellarum Australium ; 2. Tabulae Astronomicae ; 3. An Abridgment of the Astronomy of Comets. We are also indebted to Halley for the publication of several of the works of Sir Isaac Newton, who had a particular friendship for him, and to whom he frequently communicated his discoveries.