by G. H. Hardy, rev. J. J. Gray

© Oxford University Press 2004 All rights reserved

**Hobson, Ernest William** (1856-1933), mathematician, was born on 27 October 1856, at Duffield Road, Derby, the eldest son of William Hobson, founder, editor, and part proprietor of the *Derbyshire Advertiser* and a prominent figure in municipal affairs, and his wife, Josephine Atkinson. John Atkinson Hobson, the economist and publicist, was one of his brothers. His early education was obtained at Derby School. In 1871 he was elected to a scholarship at what became the Imperial College of Science, South Kensington, and studied physics for a time in London under Frederick Guthrie. Although a versatile student he was always primarily a mathematician, and in 1874 he obtained a scholarship at Christ's College, Cambridge, where he remained for the rest of his life.

Hobson was senior wrangler in January 1878 and was elected a fellow of his college in the autumn of the same year. In 1883 he was chosen as one of the first university lecturers in mathematics, and in 1903 as Stokes lecturer, a position of particular distinction. From 1910 to 1931 he was Sadleirian professor of pure mathematics. He was a conspicuous figure in international science, and received many honours including a royal medal (1907) of the Royal Society, of which he had been elected a fellow in 1893, the De Morgan medal (1920) of the London Mathematical Society, honorary degrees, and memberships of foreign academies.

Hobson's early career was not particularly distinguished. It was not until he was nearly forty that he published his first important work, an elaborate memoir on 'spherical harmonic' in the *Philosophical Transactions of the Royal Society* for 1896. A classic in its field, its preparation may well have occupied him for several years. None the less his development as a mathematician seems to have been strangely slow, and this was partly due to the Cambridge traditions of the time, namely the extravagant importance attached to position in the tripos and the general indifference to research. It was one of Hobson's greatest services to Cambridge later to help to break down these traditions.

As was then customary, Hobson served many years as a private coach for the tripos, at which he was good and successful. Although less notorious than E. J. Routh or Robert Rumsey Webb, he had one famous triumph. In 1890 one of his pupils, Philippa Fawcett, was placed above the senior wrangler in the university examinations, though as a female she could not formally contend for wrangler status. John Maynard Keynes was another of his pupils.

It was not until 1903 that Hobson abandoned coaching to do more research, and not until he was fifty that he developed fully the dominant interests of his life. The modern theory of real functions, as understood in Europe since the days of Riemann and Weierstrass, was hardly known in England before 1890. A. R. Forsyth's *Theory of Functions of a Complex Variable* (1893) raised the first interest in the subject, but Forsyth cared only for the 'complex' theory, and the more fundamental 'real' theory remained neglected; it was in work on the latter that Hobson found the great opportunity of his life. His *Theory of Functions of a Real Variable* was published in 1907. The modern theories of measure and integration, initiated in France by Bore and Lebesgue, were then still unfamiliar, and Hobson and William Henry Young (who never held a regular position in the university) were the first Cambridge mathematicians to grasp the significance of the new ideas. The subject expanded rapidly, and Hobson's book, in its various editions, occupied him for twenty years. It is a fine book, written with full mastery of a vast subject and with many important contributions of his own. Despite this, the establishment of real analysis as a research subject at Cambridge was left to his successors to accomplish.

Hobson wrote four other books. The most important is *Spherical and Ellipsoidal Harmonics* (1931): this contains much of his early work, and in particular his memoir of 1896. His earliest book, *A Treatise on Plane Trigonometry* (1891), is an important if rather elementary textbook which ran through many editions. This was the first English book, apart from the *Algebra* of George Chrystal, to give any serious account of the elements of 'algebraical analysis'. *Squaring the Circle* (1913), a reprint of six lectures given in that year, was a successful 'popular' book. In *The Domain of Natural Science* (1923), the Gifford lectures delivered at Aberdeen in 1921-2, Hobson reveals his interest in philosophy. His selection as lecturer was quite appropriate, but the book, although competent and scholarly, is slightly disappointing, the position which he defends, a rather extreme and abstract form of the 'descriptive' view of natural science, being much more reasonable than exciting.

On 1 July 1882 Hobson married Selina Rosa, daughter of Rudolf Knüsli, a merchant, of Glarus, Switzerland; they had four sons, of whom one predeceased him. Apart from his position as a leading British mathematician, Hobson was also a conspicuous and influential figure in Cambridge. He was proctor twice, served on the council of the senate and on important syndicates, and was a frequent speaker in Senate House discussions. He was regarded as a 'radical', as radicalism was understood in university circles in the early twentieth century, and he usually voted with the reformers on the university senate, the controversy over women's degrees being an exception. He was one of the leaders in the movement for the reform of the mathematical tripos which resulted in 1910 in the abolition of the Order of Merit.

Hobson died at the Evelyn Nursing Home, Cambridge, after an operation, on 18 April 1933.

G. H. HARDY, *rev.* J. J. GRAY

**Sources **

*Obits. FRS,* 1 (1932-5), 237-49

*Journal of the London Mathematical Society,* 9 (1934)

private information (1949)

personal knowledge (1949)

b. cert.

m. cert.

d. cert.

**Archives **

RS

**Likenesses **

K. Green, oils, 1925, Christ's College, Cambridge

W. Stoneman, photograph, 1926, NPG

Elliott & Fry, photograph, Christ's College, Cambridge

Maull & Fox, photograph, RS

**Wealth at death **

£28,219 *7s. 4d.:* probate, 25 May 1933, *CGPLA Eng. & Wales*

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