which he described burning mirrors composed of 'glass leaded behind,' which afterwards came into general use (Rigaud, Corr. of Scientific Men, ii. 249). The theory of equations and the search for a general method of quadratures by infinite series occupied his few leisure moments. He complains to Collins (17 May 1671) of the interruptions caused by his lectures and the inquiries of the ignorant (ib. p. 224). In the same year some members of the French Academy were desirous to obtain a pension for him from Louis XIV, but the project fell through. Gregory had never believed it serious, and easily resigned himself to its failure. Under the pseudonym of ‘Patrick Mathers, Arch-Bedal of the university of St. Andrews,’ he attacked Sinclair, ex-professor of philosophy at Glasgow, in ‘The Great and New Art of Weighing Vanity’ (Glasgow, 1672), worth remembering only for a short appendix, ‘Tentamina quædam Geometrica de Motu Penduli et Projectorum,’ giving the first series for the motion of a pendulum in a circular arc. Sinclair in his reply reproached Gregory with want of skill in the use of astronomical instruments which he had erected at St. Andrews.
Gregory was the first exclusively mathematical professor in the university of Edinburgh. He was elected on 3 July 1674, and delivered his inaugural address before a crowded audience in November. One night in the following October, while showing Jupiter's satellites to his students, he was struck blind by an attack of amaurosis, and died of apoplexy three days later, before he had completed his thirty-seventh year. He had till then enjoyed almost unbroken health. He married at St. Andrews in 1669 Mary, daughter of George Jameson [q. v.] the painter, and widow of Peter Burnet of Elrick, Aberdeen, and had by her two daughters and a son, James, afterwards professor of physic in King's College, Aberdeen (d. 1731).
Gregory's genius was rapidly developing, and the comparative simplicity of his later series showed the profit derived by him from Newton's example. Among his discoveries were a solution by infinite series of the Keplerian problem, a method of drawing tangents to curves geometrically, and a rule, founded on the principle of exhaustions, for the direct and inverse method of tangents. He independently suggested, in a letter to Oldenburg of 8 June 1675, the differential method of stellar parallaxes (Rigaud, Corresp. of Scient. Men, ii. 262; Birch, Hist. Roy. Soc. iii. 225); pointed out the use of transits of Mercury and Venus for ascertaining the distance of the sun (Optica Promota, p. 130), and originated the photometric mode of estimating the distances of the stars, concluding Sirius to be 83,190 times more remote than the sun (Geom. Pars Universalis, p. 148). The word ‘series’ was first by him applied to designate continual approximations (Commercium Epistolicum, No. lxxv). Leibnitz thought highly of his abilities (ib. No. liii), and by his desire Collins drew up an account of the inventions scattered through his correspondence (ib. No. xlvii). The collection of ‘Excerpta’ thus formed was sent by Oldenburg to Paris on 26 June 1676, and eventually found its way to the archives of the Royal Society. Most of the series sent by Gregory to Collins were included in his nephew David Gregory's ‘Exercitatio,’ and his correspondence with Newton about the reflecting telescope was reprinted as an appendix to the same writer's ‘Elements of Catoptrics’ (ed. 1735). His ‘Optica Promota’ and ‘Art of Weighing Vanity’ were republished at the expense of Baron Maseres in 1823 among ‘Scriptores Optici.’ Open and unassuming with his friends, Gregory was of warm temper, and keenly sensitive to criticism. He was devoid of ambition, and found ready amusement in the incidents of college life. A portrait of him in Marischal College shows a refined and intellectual countenance.
[Biog. Brit. iv. 1757; General Dict. v. 1737; D. Irving's Lives of Scottish Writers, ii. 239; Sir Alex. Grant's Story of the University of Edinburgh, i. 215, ii. 295; Alex. Smith's New Hist. of Aberdeenshire, i. 171, 492-3; Rigaud's Correspondence of Scient. Men in the Seventeenth Cent. ii. passim; Commercium Epistolicum, 1712, 1722, 1725, passim; Grant's Hist. of Phys. Astronomy, pp. 428, 526, 547; Hutton's Mathematical Dict. (1815); Bailly's Hist. de 1'Astr. Moderne, ii. 254, 570; Montucla's Hist. des Math. ii. 86, 376, 503; Thomson's Hist. Roy. Society, p. 289; Wolf's Gesch. der Astronomie, p. 583; Marie's Hist. des Sciences, v. 119; H. Servus's Gesch. des Fernrohrs, p. 126; Notes and Queries, 7th ser.,iii. 147; Chambers's Edinb. Journ. v. 223, 1846 (Gregory Family); Watt's Bibl. Brit.]
GREGORY, JAMES (1753–1821), professor of medicine at Edinburgh University, son of John Gregory (1724-1773) [q.v.], was born at Aberdeen in January 1753. He was educated at Aberdeen and Edinburgh, and also studied for a short time at Christ Church, Oxford. He gained considerable classical knowledge, wrote Latin easily and well, and was always ready with apt Latin quotations, which often served him well in controversy. In the winter of 1773-4 he studied at St. George's Hospital. London. While he was still a student of medicine at Edinburgh Gregory's father died suddenly during the
