STEWART, MATTHEW, D.D. a celebrated Scottish Mathematician, was the son of the Rev. Dugald Stewart, minister of Rothsay, and was born in the year '1717. At the age of seventeen, he went to Glasgow, where he studied mathematics under Dr. Robert Simson, from whom he imbibed that love of the ancient geometry which characterized his future studies. As his views in life required his attendance at the college of Edinburgh, he went there in 1741, where he attended the lectures of Colin Maclaurin. Here he devoted himself to his favourite studies, and kept tip a regular and intimate correspondence with Dr. Simson of Glasgow. In the midst of these pursuits, he was appointed to the living of Roseneath, where he completed his " General Theorems," a series of curious and interesting propositions which he pub lished in 1746, and which, though given without any demonstrations, placed the author among the geometers of the first order.* In the summer of 1746, the death of Mr. Maclaurin created a vacancy in the mathematical chair of the University of Edinburgh, and such was the superi ority over the other candidates which the General Theorems gave to Mr. Stewart, that he was elected to the office in September 1747.
In the 2d volume of the Essays of the Philosophical Society of Edinburgh, Mr. Stewart published a very neat solution of Kepler's Problem. In 1761 appeared his Tracts Physical and Mathematical, which relate to the doctrine of centripetal powers, to the theory of the lunar motions, and to the determination of the sun's distance from the earth. In 1763 he brought
out his Propositiones Geometriex more veterum demon stratx, and in the same year he published his Essay on the Sun's Distance front the Earth. In this tract he made the sun's parallax only 6".9, and conse quently his distance so much as 29,875 semi-diameters of the earth, or 118,541,428 English miles. This re sult was received with surprise, and brought forth two answers to the tract, the one by Mr. Dawson of Sudbury, and the other by Mr. Landen, who pointed out certain errors which had been committed by Mr. Stewart. To these animadversions Mr. Stewart made no reply. His health had now begun to decline, and with the view of restoring it he made a tour through England, and paid a visit to Earl Stanhope, from whom he received singular marks of attention. In 1772, when his son, Mr. Dugald Stewart, was able to lecture for him, he retired to the country, where he spent the greater part of his life. In 1775 he resigned his chair, and his son was elected joint professor with him. His health continued to decline, and he died on the 23d January 1785, at the age of 68.