# Graves, Charles (DNB01)

**GRAVES**, CHARLES (1812–1899), bishop of Limerick and mathematician, born in Dublin on 6 Nov. 1812, was youngest son of John Crosbie Graves of the Irish bar, chief police magistrate of Dublin, and of Helena, daughter of the Rev. Charles Perceval. His early education was received at a private school near Bristol. In 1829 he entered Trinity College, Dublin, and in 1832 was elected to a foundation scholarship, a distinction then given only to classical proficiency. Intended originally for the army, he became an expert swordsman and rider; he played cricket for his university, and later in life did much boating and fly-fishing. In 1834 he graduated as the first senior moderator and gold medallist in mathematics and mathematical physics. In 1836 he obtained the very rare distinction of election to a fellowship on a first candidature. In 1843 he was chosen professor of mathematics in the university of Dublin in succession to James McCullagh [q. v.] He was made dean of the Castle Chapel, Dublin, in 1860, and dean of Clonfert in 1864, and he was appointed bishop of Limerick, Ardfert, and Aguadoe in 1866, being one of the last bishops appointed before the disestablishment of the Irish church. That office he held for thirty-three years until his death.

Having been in 1837 elected a member of the Royal Irish Academy, Graves filled successively the offices of secretary of the council and secretary of the academy, and was elected its president in 1861. He was elected a fellow of the Royal Society in 1880, and the honorary degree of D.C.L. was conferred on him in 1881 by the university of Oxford. He died in Dublin on 17 July 1899 at the advanced age of eighty-six. Graves married in 1840 Selina, daughter of Dr. John Cheyne [q. v.], and by her had issue five sons and four daughters.

A monument to his memory in Limerick Cathedral bears a Latin inscription in verse by Professor R. Y. Tyrrell, with renderings in English by the bishop's son, Mr. A. P. Graves, and in Irish by Dr. Douglas Hyde. A portrait, by Miss Purser, was presented by him to the Royal Irish Academy, and an admirable profile medallion, by John Henry Foley [q. v.], belongs to his eldest son.

Graves's manners were characterised by dignified courtesy, and, in his hours of relaxation, by a genial and cordial freedom. His wide culture, keen intelligence, and conversational powers made him a very attractive and agreeable companion. His calm judgment in practical affairs was combined with admirable tact and temper. His liberal feeling towards those who differed from him won for him the esteem of all, especially in his diocese, without distinction of sect or party.

In 1841 Graves published a translation of the two elegant memoirs of Chasles 'On the General Properties of Cones of the Second Degree and of Spherical Conics.' In the copious notes appended to this translation he gave a number of new theorems of much interest, which he arrived at principally by Chasles's mode of treatment. Probably the most remarkable of these was his extension of the construction of an ellipse, as traced by a pencil which strains a thread passing over two fixed points, by substituting for the points a given ellipse, with which he showed that the locus is confocal. This he deduced from the more general theorem in spherical conics, the latter being arrived at from its reciprocal theorem—viz. if two spherical conics have the same cyclic arcs, then any arc touching the inner curve will cut off from the outer a segment of constant area. Bertrand, in his great treatise on the integral calculus (1864), attributed the foregoing fundamental theorem of Graves to Chasles, who had subsequently arrived at it by an independent investigation. In a long appendix to the volume Graves gave a method of treating curves on a sphere corresponding to the Cartesian method on the plane, arcs of great circles taking the place of right lines. This theory he worked out in detail, supplying formulae for tangents, normals, osculating circles, &c., to spherical curves. This memoir was greatly admired by Sylvester and other distinguished mathematicians, but their high expectations of its fertility have not been fulfilled.

This was the only mathematical work published by Graves. His other investigations were either embodied in his lectures as professor, or in papers read before, and published by, the Royal Irish Academy. During this period Sir William Hamilton, McCullagh, and Humphry Lloyd were also members, and the meetings were often made the occasion of announcing the results of the spirit of scientific investigation which then remarkably prevailed in the university of Dublin.

While Hamilton was explaining in a series of communications his new calculus of quaternions, several contemporary mathematicians were led to conceive more or less analogous systems, likewise involving new imaginaries. Graces proposed a system of algebraic triplets of this kind. It must, however, be said of it, as of the other similar systems, that it could not lay claim to anything like the power of the quaternions, and was not so much a valuable working method as an interesting mathematical curiosity.

Other papers by Graves, published by the Royal Irish Academy, related to the theory of differential equations, to the equation of Laplace's functions, and to curves traced on surfaces of the second degree. For example, he gave an elementary geometrical proof of Joachimsthal's well-known and fundamental theorem—viz. that at all points on a line of curvature of an ellipsoid the rectangle pd is constant, where p is the central perpendicular on the tangent plane, and d is the diameter drawn parallel to the element of the line of curvature. He also gave some very important applications of the calculus of operations to the calculus of variations, and more especially arrived at an elegant and simple demonstration, by the operational method, of Jacobi's celebrated theorem for distinguishing between maxima and minima values in the application of the calculus of variations. Graves had much literary and artistic taste, and to these were largely due the symmetry and elegance, both of method and results, which are marked characteristics of his mathematical work.

On the death of Sir William Hamilton, in 1865, Graves delivered from the presidential chair an eloquent cloge upon him containing a valuable account both of his scientific labours and of his literary attainments. As a member of the academy Graves devoted much time and thought to Irish antiquarian subjects. It is a striking instance of his varied accomplishments that, the death of George Petrie [q. v.] having taken place shortly after that of Hamilton, Graves pronounced an eloge on him also, and gave as competent a survey of the archæological researches of the one as he had given of the scientific investigations of the other. Both these 'Eloges,' originally printed in the 'Transactions of the Royal Irish Academy,' were separately published (Dublin, 1865 and 1866).

He studied with special zeal the interpretation of the ogham inscriptions, so numerous in Ireland, and applied to them the accepted methods for the decipherment of writings, known or presumed to be alphabetical, and in this way confirmed the interpretation which is given of these symbols in some of the old Irish books. He thus gave readings and renderings of a number of the inscriptions on cromlechs and other stone monuments. The subject, however, is still surrounded with difficulties, and many archaeologists have been led to the conclusion that the inscriptions are intentionally cryptic, at least in some cases.

Graves, in some 'Suggestions' published at Dublin in 1851, brought before the government the importance of having the old Irish laws, commonly called the Brehon laws, edited and translated by competent scholars. His suggestion was adopted, and he was appointed a member of the commission charged with carrying it into effect, and held this office until his death.

[Private information ; Cotton's Fasti Eccl. Hiberniæ, Suppl. p. 33.]