HAMILTON, SIR William Rowan, Irish mathematician: b. Dublin, 3 Aug. 1805; d. there, 2 Sept. 1865. He knew Greek and Latin when only six, and before he had completed his 14th year had made himself acquainted with 13 lan guages, among which were Arabic, Persian, Hindustani Sanskrit and Syriac. When 10 years old he began the study of mathematics, and at 17 presented a paper to Brinkley, the Irish astronomer-royal, which exhibited such a profound knowledge of mathematics that the latter declared the author of it to be already the first mathematician of his age. In 1827, the chair of astronomy in Trinity College, as well as the post of astronomer-royal of Ireland, be coming vacant, Hamilton obtained both appoint ments, though then only in his 23d year. His life henceforth was exclusively devoted to ab struse studies. He was knighted in 1835; in 1837 was elected president of the Royal Irish Academy, and was an honorary or correspond ing member of the principal scientific academies of Europe and America. In 1828 his of Systems of Rays' was published. In this his celebrated prediction, on theoretical grounds, of the existence of conical refraction of a ray of light was given to the world. Reasoning on the properties of light, he came to the conclu sion that under certain circumstances a ray, instead of being refracted in the ordinary way, should split up into a cone of rays; a phenome non afterward proved experimentally by Lloyd to take place under proper conditions. In 1834
his Method in Dynamics' was pub lished. In this work and that on of Rays) the whole of any dynamical problem is made to depend on a single function and its differential coefficients. Another important treatise of his is 'Algebra looked on as the Science of Pure He published also on Discontinuous Functions, or Equa tions of the Fifth Degree,' etc. But the foun dation on which his fame most securely rests is the discovery or invention of the calculus of ouaternions, an instrument of extraordinary power in the solution of intricate problems in mathematics and physics. His on Quaternions> appeared in 1853, and in 1866 a posthumous work on the same subject entitled of Consult of Sir William Rowan Hamilton,' by Graves (1883-89), with an addendum (1892); also biographies by Monck (1881) • Shinling (1865) and John Veitch (1869); and Seth, Philosophy) (1890).