by E. T. Whittaker, rev. Adrian Rice
© Oxford University Press 2004 All rights reserved
Joly, Charles Jasper (1864-1906), mathematician and astronomer, was born at St Catherine's rectory, Tullamore, Ireland, on 27 June 1864, the eldest son in the family of three sons and two daughters of John Swift Joly (successively rector of St Catherine's, Tullamore, and of Athlone), and his wife, Elizabeth, daughter of the Revd Nathaniel Slator. His father's family, of French origin, had settled in Ireland in the eighteenth century. After a short attendance at school at Portarlington, and nearly four years at Galway grammar school, Joly entered Trinity College, Dublin, in October 1882, where he won a mathematical scholarship. He graduated in 1886 with the first mathematical honour of his year--the 'studentship', candidates for which were required to offer a second subject in addition to mathematics. Joly chose physics, the experimental side of which so much interested him that he went to Berlin in order to work in Helmholtz's laboratory. The death of his father in 1887 made it necessary for him to earn a living without delay, and, abandoning a design of devoting himself wholly to experimental science, he returned to Ireland to read for a fellowship in Trinity College. The conditions of the examination discouraged strict specialism in mathematics or science, and Joly failed to win election until 1894. He then engaged in tuition at the college, and was junior proctor in 1896.
Joly's career as a productive mathematician began almost as soon as he was admitted to a fellowship. In his first paper, on the theory of linear vector functions, which was read to the Royal Irish Academy on 10 December 1894, he proved his discipleship to Sir William Rowan Hamilton, the discoverer of quaternions, and first applied the quaternionic analysis to difficult and complex problems of geometry, using it as an engine for the discovery of new geometrical properties. The properties of linear vector functions were further studied in 'Scalar invariants of two linear vector functions' (Transactions of the Royal Irish Academy, 30, 1896, 709) and 'Quaternion invariants of linear vector functions' (Proceedings of the Royal Irish Academy, 4, 1896, 1), while the extension of the quaternion calculus to space of more than three dimensions was discussed in 'The associative algebra applicable to hyperspace' (Proceedings of the Royal Irish Academy, 5, 1897, 75); the algebras considered are those that are associative and distributive, and whose units satisfy equations of the same type as the units of quaternions. Other more purely geometrical investigations were published in the Royal Irish Academy's Proceedings for 1896 and 1897 under the titles 'Vector expressions for curves' and 'Homographic divisions of planes, spheres, and space'.
On 20 March 1897 Joly married Jessie Sophia, the youngest daughter of Robert Warren Meade of Dublin. In the same year, he was appointed royal astronomer of Ireland at Dunsink observatory, where the rest of his life was spent in study and research. From 1898 to 1900 he edited Hamilton's Elements of Quaternions, originally published shortly after its author's death in 1865. Joly made considerable additions to the new edition which was published in two volumes (1899-1901). While occupied with this work, he communicated several memoirs to the Royal Irish Academy: 'Astatics and quaternion functions', 'Properties of the general congruency of curves', and 'Some applications of Hamilton's operator in the calculus of variations' were all read in 1899; in the first, quaternions are applied to the geometry of forces, in the second to pure geometry, and in the third to some of the equations of mathematical physics. Early in the following year he presented a paper entitled 'The place of the Ausdehnungslehre in the general associative algebra of the quaternion type', in which he showed that Grassmann's analysis for n dimensions, which is distributive but only partially associative, may be regarded as a limited form of the associative algebra of n+1 dimensions. Over the following five years Joly continued his work with a number of important memoirs (in the publications of the Royal Irish Academy or the Royal Society) on quaternions and geometry. One paper on 'Quaternions and projective geometry' occupied over a hundred pages in the Philosophical Transactions of the Royal Society for 1903. Finally in 1905, the centenary year of Hamilton's birth, he brought out A Manual of Quaternions, which at once superseded all other introductory works on the subject.
As royal astronomer Joly directed much observational work, the fruits of which appeared in the Dunsink Observations and Researches. In 1900 he accompanied an eclipse expedition to Spain, and obtained some excellent photographs of totality; an account of the results was published in the Transactions of the Royal Irish Academy (32, 1902-4, 271). He also edited Thomas Preston's Theory of Light (3rd edn, 1901).
Joly was elected fellow of the Royal Astronomical Society in 1898 and FRS in 1904. He was also a trustee of the National Library of Ireland and president of the International Association for Promoting the Study of Quaternions. He was fond of climbing, being a member of the Alpine Club from 1895. In literature he was well versed in Dante's work. He died at the observatory, of pleurisy following typhoid fever, on 4 January 1906 and was buried at Mount Jerome cemetery, Dublin. His wife and three daughters survived him.
E. T. WHITTAKER, rev. ADRIAN RICE
Sources
personal knowledge (1912)
private information (1912)
J. J. and R. S. B., PRS, 78A (1907), lxii-lxix
Monthly Notices of the Royal Astronomical Society, 66 (1905-6), 177-8
G. Scriven, 'In memoriam: C. J. Joly', Alpine Journal, 23 (1906), 58
Wealth at death
£797 11s. 3d.: Irish administration sealed in London, 21 May 1906, CGPLA Eng. & Wales
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