JOHN**, an eminent mathematician and antiquary, was the eldest son of John Greaves, rector of Colemore, near Alresford in Hampshire, and born in 1602. He was educated at Balliol College, Oxford, from which he removed to Merton. He was afterwards, on the ground of merit, chosen professor of geometry in Gresham College. His ardent thirst of knowledge soon led him to visit several parts of Europe, where he eagerly availed himself of every opportunity to improve it. His travels were next into the countries of the East, where nothing remarkable seems to have escaped his observation. With indefatigable industry, and even at the peril of his life, he collected for Archbishop Laud a considerable number of Arabic, Persian, and Greek manuscripts, of which he well knew the value, as he was a master of the languages in which they were written. He also collected for that prelate many oriental gems and coins. He made a more accurate survey of the pyramids of Egypt than any traveller who had preceded him, and afterwards digested his observations in a work on that subject. On his return from the East, he visited a second time several parts of Italy; and during his stay at Rome instituted inquiries into the ancient weights and measures. Soon after his return he was appointed to the Savilian professorship of astronomy at Oxford; an office for which he was eminently qualified, as the works of the ancient and modern astronomers were alike familiar to him. But, after enjoying this preferment for some time, Greaves was deprived of it by the parliamentary visitors, on account of his strong royalist predilections, and died on the 8th of October 1652, of a fatal disorder, which appears to have been brought on by excessive application. Besides his papers in the Philosophical Transactions, the works of Greaves printed separately are, 1. *Pyramidologia*, or a description of the Pyramids in Egypt, London, 1646, in 8vo; 2. A Discourse of the Roman Foot and Denarius, ibid. 1649, in 4to; 3. Elementa Linguae Persicae, ibid. 1649, in 4to; 4. Epochen celebriorum Astronomorum, Historicorum, Chronologis Chataiorum, Syro-Greecorum, Arabum, Persarum, &c. usitatae, ex traditione Ulug Beig, Arab. et Lat. London, 1650, in 4to; 5. Chorasmiae et Mawarnanabrag, hoc est, Regionum extra fluvium Oxum, descriptio, ibid. 1650; 6. Astronomicae quadam, ex traditione Shah Cholqii Persae, una cum hypothesibus Planetarum, ibid. 1652, in 4to. In 1737, Dr Birch published the Miscellaneous Works of Greaves, in two vols. 8vo, containing some of those above mentioned, with additions, and a biographical notice of the author.