Ernest William Hobson

RAS obituary

ERNEST WILLIAM HOBSON was one of the most distinguished Fellows of the Society. Beginning his career at Cambridge at a time when some knowledge of lunar and planetary theory was expected of all its mathematical residents, he gave considerable study to the subject over many years; and his interest in the logical formulation of dynamical theory never left him. Senior Wrangler in 1878, he was very soon engaged as a Mathematical Lecturer at Christ's College; in 1884 he was chosen as one of the four who were distinguished by the title of University Lecturers, the other three being Mr. Glazebrook, Mr. J. J. Thomson and Mr. Forsyth (Reporter, June 3). He became a member of the London Mathematical Society in 1887, and published the first of his papers in their Journal in 1888. This, on the conduction of heat, indicates the character of his work in those days, which became a study of the functions used in the mathematical physics and astronomical theory of that time. To mathematicians, the acumen and thoroughness with which, up to the end of his life, he influenced the analytical theory of such modes of expression needs no remark. But already, in the last decade of the century, his mind was turning from the applications of these functions to the logical theory of the functions themselves. In 1893 Dr. Forsyth, who as the Senior Wrangler of 1881 was specially distinguished for his knowledge of Hydrodynamics, had created a school of Mathematical Analysis in Cambridge, by the publication of his volume, of more than 600 royal octavo pages, on functions of a complex variable. In 1902 Hobson carried the change still further back to fundamentals, by his Presidential Address to the London Mathematical Society, on the Infinite and Infinitesimal in Mathematical Analysis. Those who were present must still remember the silence as he solemnly pronounced the words, "This was the first breach in the Infinite"; and those who knew him had often heard of the impression which the volume of Louis Couturat, De l'infini mathématique (1896), had made upon him. In 1903 Hobson became Stokes lecturer. In 1910 he became Sadleirian Professor of Pure Mathematics; and added, to the subjects on which he gave lectures, that of Calculus of Variations, which his predecessor in the Chair had introduced; this office he resigned in 1931. In 1907 he published one large volume, The Theory of Functions of a Real Variable; the second edition of this in two volumes, 1920 and 1925, contains in all 1450 royal octavo pages; another volume, The Theory of Spherical and Ellipsoidal Harmonics, published in 1931 (500 pp., royal 8vo), applied to these functions the results of one of his great original papers, on the "Theory of Convergence." Less fundamental are his Treatise on Plane Trigonometry (1891), and his little volume on Squaring the Circle (57 pp., 1913), and two lectures delivered respectively at University College and at King's College, London. His Gifford Lectures at Aberdeen, on the Domain of Natural Science (1921-22), has reached a second edition; it illustrates well the catholicity of his interest and the penetration of his intellect; its earlier part is a careful exposition of his judgment of the limitations to which the contribution of natural science to our knowledge of the universe is necessarily subject. In 1912 he was a Secretary of the International Mathematical Congress held at Cambridge; in the same year he was President of Section A, at the meeting of the British Association in Sheffield.

He died on 1933 April 18.
He was elected a Fellow of the Society on 1895 June 14.

Ernest William Hobson's obituary appeared in Journal of the Royal Astronomical Society 94:5 (1934), 376-377.