See A. M. Bernasconi, _Acta Gregorii Papae XVI. scilicet constitutiones, bullae, litterae apostolicae, epistolae_, vols. i-4 (Rome, 1901 ff.); Cardinal Wiseman, _Recollections of the Last Four Popes_ (London, 1858); Herzog-Hauck, _Realencyklopadie_, vol. vii. (Leipzig, 1899), 127 ff. (gives literature); Frederik Nielsen, _History of the Papacy in the 19th Century_, ii. (London, 1906). (W. W. R.*) GREGORY,[1] the name of a Scottish family, many members of which attained high eminence in various departments of science, fourteen having held professorships in mathematics or medicine. Of the most distinguished of their number a notice is given below. I. DAVID GREGORY (1627-1720), eldest son of the Rev. John Gregory of Drumoak, Aberdeenshire, who married Janet Anderson in 1621. He was for some time connected with a mercantile house in Holland, but on succeeding to the family estate of Kinardie returned to Scotland, and occupied most of his time in scientific pursuits, freely giving his poorer neighbours the benefit of his medical skill. He is said to have been the first possessor of a barometer in the north of Scotland; and on account of his success by means of it in predicting changes in the weather, he was accused of witchcraft before the presbytery of Aberdeen, but he succeeded in convincing that body of his innocence. II. JAMES GREGORY (1638-1675), Scottish mathematician, younger brother of the preceding, was educated at the grammar school of Aberdeen and at Marischal College of that city. At an early period he manifested a strong inclination and capacity for mathematics and kindred sciences; and in 1663 he published his famous treatise _Optica promota_, in which he made known his great invention, the Gregorian reflecting telescope. About 1665 he went to the university of Padua, where he studied for some years, and in 1667 published _Vera circuli et hyperbolae quadratura_, in which he discussed infinite convergent series for the areas of the circle and hyperbola. In the following year he published also at Padua _Geometriae pars universalis_, in which he gave a series of rules for the rectification of curves and the mensuration of their solids of revolution. On his return to England in this year he was elected a fellow of the Royal Society; in 1669 he became professor of mathematics in the university of St Andrews; and in 1674 he was transferred to the chair of mathematics in Edinburgh. In October 1675, while showing the satellites of the planet Jupiter to some of his students through one of his telescopes, he was suddenly struck with blindness, and he died a few days afterwards.