which might be made of similar phenomena in the determination of the sun’s distance from the earth. He first observed the necessity of shortening the pendulum as it approached the equator; or, at least, when Hook afterwards mentioned the circumstance to Newton, it was the first time the latter had heard of the fact. Soon after his return to England, in November, 1678, Halley obtained the degree of M.A. from the University of Oxford, by royal mandate, and was elected Fellow of the Royal Society. This body had been requested by Hevelius to select some person who might add the southern stars to his catalogue. A dispute was also pending between him and Hook, as to the use of telescopes in observing the stars, to which the former objected. To aid Hevelius, as well as to decide upon the character of his observations, Halley went to Dantzic, and it is related, as a proof of the energy of his character, that in one month from the time of his landing in England he published his catalogue, procured a mandate, took the degree, was elected F.R.S., arranged to go to Dantzic, and wrote to Hevelius. He arrived on the 26th of May, 1679, and the same night entered upon a series of observations with Hevelius, which he continued till July, when he returned to England, fully satisfied of his coadjutor’s accuracy. In 1680 he again visited the continent. Between Paris and Calais he had a sight of the celebrated comet of that year, well known as the one by observations of which the orbit of these bodies was discovered to be nearly a parabola. He returned from his travels in the year 1681, and shortly after married the daughter of a Mr. Tooke then Auditor of the Exchequer, which union lasted fifty-five years. He settled at Islington, where, for more than ten years, he occupied himself with his usual pursuits, of the results of which we shall presently speak more particularly. In 1691 the Savilian Professorship of Astronomy became vacant, and, as Whiston relates, on the authority of Dr. Bentley, Bishop Stillingfleet was requested to recommend Mr. Halley. But the astronomer’s avowed disbelief of Christianity interfered with his election in this instance, and the Professorship was given to Dr. Gregory. It is related by Sir David Brewster that Halley, when inclined to enter upon religious subjects with Newton, always received a check in words like the following, “You have not studied the subject—I have.”