# O'Brien, Matthew (DNB00)

**O'BRIEN**, MATTHEW (1814–1855), mathematician, was born at Ennis in 1814, the son of Matthew O'Brien, M.D. He entered Gonville and Caius College, Cambridge, as a scholar in 1834, and graduated third wrangler in the mathematical tripos of 1838 (M.A. 1841). He became junior fellow of his college in 1840, but resigned his fellowship in the following year. He was moderator in the mathematical tripos for 1843 and 1844. He was lecturer in practical astronomy in the Royal Military Academy, Woolwich, from 10 Jan. 1849 till his death, and professor of natural philosophy and astronomy in King's College, London, from 8 March 1844 to 17 Aug. 1854. He died in Petit Ménage, Jersey, on 22 Aug. 1855.
He was the author of two elementary text-books—on ‘Differential Calculus’ (1842), and on ‘Plane Co-ordinate Geometry’ (1844). In the former of these he makes exclusive use of the method of limits. He published ‘Solutions to the Senate-House Problems for 1844;’ ‘Lectures on Natural Philosophy,’ given at Queen's College, London (1849); and ‘A Treatise on Mathematical Geography,’ being part i. of ‘A Manual of Geographical Science’ (1852). He also wrote some tracts on mathematical questions connected with astronomy, in which he claimed a certain latitude in the symbolic use of divergent series.

[O'Brien's Works; information kindly supplied by Dr. Venn; Gent. Mag. 1855, ii. 551.]