DAVID GREOORY was the son ofJamesOregory'a elder brother David, a remarkable man, skilled in medicine, philosophy, and mathematics, and the first person, it is said, who possessed a barometer in Scotland. (Hutton, 'Math. Diet.') David Gregory was born at Aberdeen iu 1661, and there received the early part of his education, which was completed at Edinburgh. The possession of his uncle's papers is said to have determined his bias to mathematics. At the age of twenty three he was appointed to the chair of mathematics at Edinburgh which his undo had formerly held, and he has the distinguished merit of being one of the first public teachers who introduced the Newtonian philosophy into their schools. In 1691 he was chosen Savilieu pro fessor of astronomy at Oxford, and admitted to the degree of 31.D He died October 10th 1708, leaving unfinished an edition of the Conies of Apollonius, which was completed by Halley.
David Gregory was a skilful and elegant mathematician, but inferior to his uncle in inventive genius. His chief works are :—'Exereitatio Geometries do Dimensione Figurarum, &c.; Edinb., 1684; 'Catoptricas et Dioptricee Sphwricas Elementa,' Oaf., 1695, republished in English; 'Astronomias Physiere et Geometricas Elements,' Oxf., 1702. " This
is accoonted his masterpiece. It is founded on the Newtonian doctrines, and was esteemed by Newton himself as a most excellent explanation nod defence of his philosophy" (Hutton). This work appeared between the first and emend editions of the 'Priocipia,' and Newton took the opportunity of inserting an account of the improvements which he had made since the publication of the first edition. Euclidis qua: aupersunt Ginnie,' Gr. and Lat., Oxf., 1703.
It is remarkable that himself and two brothers were at the same time mathematical professors in three universities. Janes GREGORY succeeded him at Edinburgh in 1691. CHARLES GREGORY was appointed mathematical professor at St. Aodrews in 1707, and, resigning in 1739, was succeeded by his son, another David Gregory. Dr. Reid, professor of moral philosophy at Glasgow, was a nephew of these brothers.
Returning to the elder branch of the family : James Gregory, in ventor of the telescope, had one eon, JAMES, born in 1674, who became professor of medicine in King's College, Aberdeen. He was the father of JAMES GREGORY, M.D., who succeeded him in his professorship, and of