by A. J. Crilly

© Oxford University Press 2004 All rights reserved

**Murphy, Robert** *(bap.* 1807, *d.* 1843), mathematician, was born in Beecher Street, Mallow, in the north of co. Cork, and baptized on 8 March 1807 into the Church of Ireland, in Mallow, the sixth child of seven boys and two girls of John Murphy *(d.* 1814), shoemaker and parish clerk in Mallow, and his wife, Margaret *(d.* 1832). He showed little interest in his father's craft but preferred reading. In 1817 the eleven-year-old was run over by a cart outside his home and he spent eighteen months recuperating from a fractured thigh bone. During convalescence he occupied himself with solving 'cuts' from a Cork almanac where the originality of his submitted solutions caught the attention of Mulcahy, a well-known tutor, who hastened to Mallow to meet the anonymous problem-solver. Amazed to find a boy on crutches, Mulcahy delivered his verdict: 'you have a second Sir Isaac Newton in Mallow: pray look after him' (De Morgan, 337). Murphy was saved from the cobbler's trade and between 1819 and 1823 received a classical education in Mr Hopley's school in Mallow, free of charge.

In 1824 Murphy published a pamphlet refuting John Mackey's published claim that a method for 'duplicating the cube' had been found (a deceptively deep mathematical problem of constructing a cube of twice the volume of a given cube using only the methods of Euclidean geometry). Without sufficient grounding in the classics, Murphy failed to gain entry to Trinity College, Dublin, but Robert Woodhouse, who had dismissed a recommendation that Murphy be accepted at Cambridge, reversed his decision on closer study of Murphy's pamphlet. Murphy was admitted on 7 July 1825 at Gonville and Caius College; his backers in Mallow had provided money for the first year but subsequently Murphy accepted college loans. In January 1829 he graduated BA as third wrangler in the mathematical tripos, proceeding MA in 1832.

In May 1829 Murphy was elected to a Perse fellowship of Caius; on 4 June 1831 he was ordained deacon in the Church of England (Chichester) and in 1831-3 was junior dean responsible for student discipline. He conducted original research and his Cambridge career seemed assured. However, he soon found himself in financial difficulty, his inability to handle what little money he had being compounded by his natural generosity. One of his first acts on gaining his fellowship was to reimburse Hopley's widow for the education he received in Mallow. Moreover, he acquired 'dissipative habits' which included an appreciation of the college wine cellar, and gambling. Murphy supplemented his meagre income with such unlikely college appointments as Hebrew lecturer (1830-35) and Greek lecturer (1832). On surer ground he was a university examiner in mathematics (1833).

Murphy was a widely respected mathematician. He was a member of the Cambridge Philosophical Society (1830-35) and served on its council (1832, 1835). His early scientific work lay in integral transforms and their application to electrostatics. On a suggestion of William Whewell, Murphy wrote *Elementary Principles of the Theories of Electricity, Heat, and Molecular Actions* (1833), designed for Cambridge students. It contained new material and cited the work of Poisson and Ampère. Murphy recognized the importance of George Green's celebrated '1828 Essay' which was eventually published in *Crelles Journal.* Few writers gave the mathematical theory of electricity so thoroughly and clearly as Murphy, and forty years on William Thomson remarked that Murphy's account still satisfied him.

On 5 June 1834 Murphy was elected to the Royal Society. In the same year he was promoted to a Frankland junior fellowship with an income of £25 per half-year. In July 1835 he hoped to be a candidate for the prestigious Cambridge Plumian chair made vacant by George Biddell Airy's appointment as astronomer royal, but James Challis was elected and Murphy, perhaps seeing his ambition blocked, returned to Ireland in the new year.

Murphy was drawn back to England in October 1836 when he heard that G. J. Pelly White, professor of mathematics at University College, London, had drowned off Sark. He did not know Augustus De Morgan had been appointed to the chair (for the second time). Murphy was reduced to living in cheap lodging houses, earning a scanty living by writing and taking private pupils. De Morgan made arrangements for him to write for the Society for the Diffusion of Useful Knowledge and supply popular articles for Charles Knight's *Penny Cyclopaedia.* In these surroundings, Murphy published two papers in the *Philosophical Transactions of the Royal Society.* In the second he set out the theory of differential operators and delineated the principal ideas in the calculus of operations, including non-commutative ones, a calculus which fuelled Boole's and Cayley's work in invariant theory.

Desperate for money and abandoned by his pupils, Murphy wrote *A Treatise on the Theory of Algebraical Equations* (1839, repr. 1847). It was more than a textbook and after Murphy's death De Morgan inscribed his copy: 'He kept body and soul together while writing it--and, I think, did the same for the subject' (Smith, 4). Murphy maintained his connection with Gonville and Caius and in 1838 was promoted to another junior fellowship (£95 per half-year). He believed his luck had changed when he was appointed as examiner in mathematics and natural philosophy in London University (£200 for sixteen days of examining) in October but his hopes of a senior fellowship at Caius remained illusive.

Murphy is a tragic figure in the history of mathematics. His twenty-two publications on electricity and pure mathematics received attention from contemporaries, and had he led a stable life, and not suffered from his 'illness' (possibly alcoholism), he would surely have taken a leading place in a Cambridge school of mathematics. He died of consumption on 12 March 1843 at 21 East Street, Holborn.

A. J. CRILLY

**Sources **

G. D. Smith, 'Robert Murphy', *History of Mathematics, Monash University,* 31 (July 1984)

L. Creedon, 'The life and work of Robert Murphy', MSc diss., University College, Cork, 1992

[A. De Morgan], 'Robert Murphy', *Supplement to the Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge,* 2 (1846), 337-8

D. M. Cannell, *George Green: mathematician and physicist, 1793-1841* (1993)

J. J. Cross, *Integral theorems in Cambridge mathematical physics, 1830-1855,* ed. P. M. Harman (1985), 112-48

E. Koppelman, 'The calculus of operations and the rise of abstract algebra', *Archive for History of Exact Sciences,* 8 (1971-2), 155-242

*Mallow Field Club Journal,* 7 (1989)

Venn, *Alum. Cant.*

J. Venn and others, eds., *Biographical history of Gonville and Caius College,* 2: *1713-1897* (1898)

*Catalogue of scientific papers,* Royal Society, 4 (1870), 554

R. Murphy, *Refutation of a pamphlet written by the Rev. John Mackey* (1824)

R. Murphy, *A treatise on the theory of algebraical equations* (1839)

D. Barry, 'Robert Murphy: mathematician of true genius', *Mallow Field Club Journal,* 4 (1986)

**Archives **

BL, letters to Charles Babbage, Add. MSS 37186-37201

UCL, letters to the Society for the Diffusion of Useful Knowledge

**Likenesses **

J. Woodhouse, portrait, repro. in *Gonville and Caius College, Cambridge painted (c.1828)*

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