328 PHILOSOPHICAL TRANSACTIONS. [anNO I676. 



method ; where, besides observations, nothing more is supposed, than that the 

 orbits of the planets be elHptical, that the sun be in their common focus, and 

 in fine, that their periods be discovered in such a manner as that no sensible 

 error can arise, at least in two or three revolutions. 



These things being granted, let S be the sun, fig, 5, pi. 10, ABCDE, the 

 orbit of the earth ; P the planet Mars, which is to be preferred on many ac- 

 counts ; and in the first place let the true time and place wherein Mars is in 



sciences, astronomy, geometry, and algebra, optics and dioptrics, ballistics and artillery, speculative 

 and experimental philosophy, natural history, antiquities, philology, and criticism 3 all abounding with 

 ideas new, singular and useful. 



In 1691 } the Savilian professorship of astronomy at Oxford being vacant, Mr. Halley applied for 

 that office, but without success : refusing to deny or conceal his sceptical turn of mind, though his 

 own extraordinary merits were supported by the interest of Newton, he was rejected, and tlie office 

 bestowed on Dr. Gregory. In 1698 he procured from King William the appointment of captain of 

 a ship, sent out for the express purpose of establishing his theory of the variation of the compass, 

 which he had advanced in l683. He made another voyage on the same design tlie year following, 

 and returned to England in September 1700, with numerous observations; from whence he soon 

 after published his general chart, exhibiting at one view the variation of the compass in all these seas 

 where the English navigators were acquainted. He was also soon after sent out again on a third 

 voyage, to ascertain the course of the tides in every part of the British channel, of which, in 1702, 

 he published a large chart. Soon after, at the request of the Emperor of Germany, he made two 

 journeys, to inspect the coasts of the Adriatic Sea, and to examine certain ports, which tlie emperor 

 intended to construct or improve. He returned in 1703, when he was appointed to succeed Dr. 

 Wallis as professor of geometry at Oxford, and was at the same time honoured with the degree of 

 doctor of laws. Here he soon employed himself in translating into Latin, from the Arabic, Apol- 

 lonius's Section of a Ratio, and in restoring tlie same author's two last books on the Section of a 

 Space, from tlie account given of them by Pappus; which were published in 1706. He next pre- 

 pared an edition of the whole works of ApoUonius, and ventured to supply the whole 8th book of the 

 Conies, the original of whicb was lost. To this he added, Serenus on the Sections of the Cylinder 

 and Cone, in Greek, with a Latin translation ; and published the whole in 1710. Besides these, the 

 Miscellanea Curiosa, in 3 volumes Svo, had come out under his direction, in 1708, consisting 

 chiefly of pieces of his own, extracted from the Philosophical Transactions. 



In 1713, Dr. Halley succeeded Sir Hans Sloane, in the office of Secretary to the Royal Society; 

 which he resigned in 1721, having been appointed Astronomer Royal on the decease of Mr. Flam- 

 steed in 1719. And although he was now 63 or 64- years of age, yet here for the space of 18 years 

 he watched the heavens with the closest attention, hardly ever missing an observation, and, without 

 any assistant, performed the whole business of tlie observatory himself. 



About 1737 he was seized with a paralytic disorder in one of his hands. However, he still con- 

 tinued to come regularly once a week, to meet his friends in town on Thursdays, before the meet- 

 ing of the Royal Society, at what is still called Dr. Halley's club. But his paralytic disorder in- 

 creasing, his strength gradually decreased, till he expired Jan. 14, 1742, in the 86th year of his age; 

 aiid his corpse was interred in the church-yard of Lee, near Blackheath. — Beside the works before- 

 mentioned. Dr. Halley's principal publications are, 1. Catalogus Stellarum Australium. 2. Tabulae 

 Astronomicae. 3. The Astronomy of Comets. Witli a multitude of papers in the Philosophical 

 Transactions, from volume xi to volume Ix. 



