Chapter III: DAVID GREGORY (1661-1708), son of David Gregory (1627-1720), was

born in Aberdeen and educated partly in his native city and partly in Edinburgh, where he became professor of mathematics in 1683. From 1691 till his death he was Savilian professor of astronomy at Oxford. His principal works are _Exercitatio geometrica de dimensione figurarum_ (1684), _Catoptricae et dioptricae sphaericae elementa_ (1695), and _Astronomiae physicae et geometricae elementa_ (1702)--the last a work highly esteemed by Sir Isaac Newton, of whose system it is an illustration and a defence. _A Treatise on Practical Geometry_ which he left in manuscript was translated from the Latin and published in 1745. He was succeeded in the chair of mathematics in Edinburgh by bis brother James; another brother, Charles, was in 1707 appointed professor of mathematics in the university of St Andrews; and his eldest son, David (1696-1767), became professor of modern history at Oxford, and canon and subsequently dean of Christ Church.