# Dictionary of National Biography, 1901 supplement/Casey, John

​CASEY, JOHN (1820–1891), mathematician, born at Kilkenny, co. Cork, in May 1820, was the son of William Casey. He was educated at first in a small school in his native village, and afterwards at Mitchelstown. He became a teacher under the board of national education in various schools, including Tipperary national school, and ultimately head-master of the central model schools, Kilkenny. He turned his attention to mathematics, and succeeded in solving Poncelet's theorem geometrically. This solution led him into correspondence with Dr. Salmon and Richard Townsend (1821-1884) [q.v.] At Townsend's suggestion he entered Trinity College, Dublin, in 1858, obtaining a sizarship in 1859 and a scholarship in 1861, and graduating B.A. in 1862. From 1862 till 1873 he was mathematical master in Kingstown school. On 14 May 1866 he was elected a member of the Royal Irish Academy, and in March 1880 became a member of its council. In 1869 he received from Dublin University the honorary degree of LL.D. In 1873 he was offered a professorship of mathematics at Trinity College, but with some reluctance he chose rather to ​assist the advancement of Roman catholic education by accepting the professorship of higher mathematics and mathematical physics in the Catholic University. He was elected a member of the London Mathematical Society on 12 Nov. 1874, a fellow of the Royal Society of London on 3 June 1875, and a member of the Sociéte Scientifique de Bruxelles in 1878. In 1878 the Royal Irish Academy conferred on him a Cunningham gold medal. In 1881 the Norwegian government presented him with Niels Henrik Abel's works.
In 1881 Casey relinquished his post in the Catholic University, and was elected to a fellowship in the Royal University, and to a lectureship in mathematics in University College, Stephen's Green, which he retained until his death. In 1881 he began a series of mathematical class-books, which have a high reputation. He was elected a member of the Société Mathematique de France in 1884, and received the honorary degree of LL.D. from the Royal University of Ireland in 1885. He died at Dublin on 3 Jan. 1891.
Casey's work was chiefly confined to plane geometry, a subject which he treated with great ability. Professor Cremona speaks with admiration of the elegance and mastery with which he handled diificult and intricate questions. He was largely self-taught, but widened his knowledge by an extensive correspondence with mathematicians in various parts of Europe.
Casey was the author of:
* 'On Cubic Transformations' ('Cunningham Memoirs of the Royal Irish Academy,' No. 1), Dublin, 1880, 4to.
* 'A Sequel to Euclid' (Dublin University Press Series), Dublin, 1881, 8vo; 6th edit, by Patrick A. E. Dowling, 1892.
* 'A Treatise on the Analytical Geometry of the Point, Line, Circle, and Conic Section' (Dublin University Press Series), Dublin, 1885, 8vo; 2nd edit, by Dowling, 1893.
* 'A Treatise on Elementary Trigonometry,' Dublin, 1886, 8vo; 4th edit, by Dowling, 1895.
* 'A Treatise on Plane Trigonometry, containing an Account of Hyperbolic Functions,' Dublin, 1888, 8vo.
* 'A Treatise on Spherical Trigonometry,' Dublin, 1889, 8vo.
He edited 'The First Six Books of Euclid' (Dublin, 1882, 8vo; 11th edit. 1892), and was the author of eighteen mathematical papers between 1861 and 1880, enumerated in the Royal Society's 'Catalogue of Scientific Papers.' From 1862 to 1868 he was one of the editors of the 'Oxford, Cambridge, and Dublin Messenger of Mathematics,' and for several years was Dublin correspondent of the 'Jahrbuch Uber die Fortschritte der Mathematik.'
[Proceedings of the Royal Soe. 1891, vol. xlix. pp. xxiv-xxv; information kindly given by J. K. Ingram, esq., LL.D.]
E. I. C.