this was his last effort; he was seized with faintness and a chill, and died at Ballykilbeg on 17 July 1902. He was buried in Rathmullan churchyard on 21 July; a monument over his grave was erected by public subscription. He was thrice married: (1) on 22 Feb. 1853 to Harriet, daughter of Robert Allen of Kilkenny, by whom he had issue two sons and two daughters; (2) on 10 Oct. 1861 to Arminella Frances, daughter of Thomas Drew, D.D.; (3) in 1863 to Georgiana Barbara (*d*. 1900), youngest daughter of Sir John Hay of Park, seventh baronet, by whom he had issue three sons and four daughters. His portrait adorns many Orange banners.

Although a man with a mission, Johnston was a gentleman in grain, 'transparently upright and honest,' and simply and devoutly rehgious. He never lost the esteem of his opponents. The Belfast nationalist organ, in recording his death, spoke of his 'courage and consistency,' adding that he was 'loved by his catholic tenants and neighbours.' One of his daughters joined the Roman catholic church, and it was characteristic of his sense of duty and his goodness of heart that he drove her to mass on the way to his own parish church. He contributed from time to time to various journals but he was not distinguished as a writer; his separate literary efforts were early, and of no great moment. He published: 1. 'Nightshade: a Novel,' 1857 ; 2nd edit. 1858. 2. 'Ribbonism and its Remedy: a Letter,' Dublin, 1858. 3. 'Freshfield,' 1859 (a novel). 4. 'Under which King?' 1872 (a story).

[Belfast News-Letter, 18 and 22 July 1902; Northern Whig, 18 and 22 July 1902; Irish News and Belfast Morning News, 18 July 1902; Burke's Landed Gentry of Ireland, 1904; information from Mr. John McBride, Holywood, co. Down; personal recollections.]

**JOLY**, CHARLES JASPER (1864–1906), royal astronomer of Ireland, born at St. Catherine's rectory, Tullamore, on 27 June 1864, was 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, by his wife Elizabeth, daughter of the Rev. Nathaniel Slator. His father's family, of French origin, settled in Ireland in the eighteenth century. After a short attendance at school at Portarlington, and nearly four years at Galway grammar school, Joly in October 1882 entered Trinity College, Dublin, 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 rendered it needful for him to seek a competency 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 till 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 Dec. 1894, he proved his discipleship to Sir William Rowan Hamilton [q. v.], 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' (*Trans. R.I.A.* 1896, xxx. 709) and 'Quaternion invariants of linear vector functions' (*Proc. R.I.A*. 1896, iv. 1), while the extension of the quaternion calculus to space of more than three dimensions was discussed in 'The associative algebra applicable to hyperspace' (*Proc. R.I.A.* 1897, v. 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 about this time under the titles 'Vector expressions for curves' (*Proc, R.I.A.* 1896, iv. 374) and 'Homographic divisions of planes, spheres, and space' (*Proc. R.I.A.* 1897, iv. 515).

In 1897 Joly resigned his work at Trinity College on his appointment as royal astronomer of Ireland at Dunsink observatory, where the rest of his life was spent. In this quiet retreat Joly devoted himself to advanced study and research. From 1898 to 1900 he was engaged in editing Hamilton's 'Elements of Quaternions,' originally published shortly after its author's death in 1865, and now out of