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HODGKINSON, EATON (1789–1861), writer on the strength of materials, the son of a farmer, was born at Anderton in the parish of Great Budworth, Cheshire, on 26 Feb. 1789. He was left fatherless when six years old, but his mother carried on the farm, and was able to send him to Northwich grammar school, where he received the rudiments of a classical education, and afterwards to Mr. Shaw's private school in the same town, where his natural bias for mathematics was allowed full scope. His mother's difficulties compelled her to abandon an intention of educating him for the church, and he devoted himself to the farm. For that vocation he was unsuited, and he persuaded his mother to embark her little capital in a pawnbroking business at Salford, Manchester. Removing thither in 1811, when he was twenty-two years old, he soon took up the line of scientific inquiry which was suited to his genius, and became acquainted with John Dalton and other gifted men then living at Manchester. In March 1822 he read a paper ‘On the Transverse Strain and Strength of Materials’ before the Literary and Philosophical Society (printed in their Memoirs, vol. iv. 2nd ser.). In this contribution is recorded an element which became an important object in all his subsequent experiments, namely ‘set,’ or the difference between the original position of a strained body and the position it assumes when the strain is removed. He fixed the exact position of the ‘neutral line’ in the section of rupture or fracture, and made it subservient to the computation of the strength of a beam of given dimensions. His conception of the true mechanical principle by which the position of the line could be determined has long obtained general acceptance. In 1828 he read before the same society an important paper ‘On the Forms of the Catenary in Suspension Bridges,’ and in 1830 one on ‘Theoretical and Practical Researches to ascertain the Strength and best forms of Iron Beams,’ one of the most valuable contributions to the history of the strength of materials ever made. From the theoretical expositions there given of the neutral line, the experiments to determine the strongest beam were devised and successfully carried out, resulting in the discovery of what is known as ‘Hodgkinson's beam,’ which has been described as the pole star for engineers and builders. Among his other contributions to the British Association are two on the temperature of the earth in the deep mines of Lancashire and Cheshire (Reports, 1839–40). In the ‘Philosophical Transactions’ for 1840 he wrote ‘On the Strength of Pillars of Cast Iron and other Materials,’ which secured him the royal medal of the Royal Society and his election as F.R.S. He rendered important service to Robert Stephenson in the construction of the Conway and Britannia tubular bridges by fixing the best forms and dimensions of tubes. He edited the fourth edition of Tredgold's work on the strength of cast iron, 1842, and published a volume of his own, ‘Experimental Researches on the Strength and other Properties of Cast Iron,’ in 1846. Many of the experiments were, as he states in his preface, carried out at the works of Mr. W. Fairbairn. He worked from 1847 to 1849 as one of the royal commissioners to inquire into the application of iron to railway structures. His own contributions to the commissioners' report occupy a prominent position, and elicited the special thanks of his fellow-commissioners. In 1847 he was appointed professor of the mechanical principles of engineering at University College, London, where, however, his lectures were deprived of a large share of efficiency by his nervous hesitancy of speech. He was a member of the Geological Society and of the Royal Irish Academy, and honorary member of the Institute of Civil Engineers (elected 1851) and of other societies. From 1848 to 1850 he was president of the Manchester Literary and Philosophical Society.

He was twice married, but had no children. His first wife was Catherine, daughter of the Rev. William Johns of Manchester; his second the daughter of Henry Holditch, captain in the Cheshire militia. In his last years, when he had become enfeebled both physically and mentally, he occupied himself in arranging his papers with a view to their publication in a collected form, but he did not live to complete the task. He died at Higher Broughton, Manchester, on 18 June 1861, and was buried at his native village.

[Life, by R. Rawson, in Memoirs of Manchester Lit. and Phil. Soc. 3rd ser. ii. 145; also in Smithsonian Report for 1868; Proc. of Institute of Civil Engineers, xxi. 542; Todhunter's Hist. of the Elasticity and Strength of Materials, 1886, vol. i.; Pole's Life of Sir W. Fairbairn, 1877; R. Angus Smith's Centenary of Science in Manchester, 1883. The Royal Society's Catalogue of Scientific Papers gives a list of nineteen papers by Hodgkinson. A summary of his experiments will be found in Barlow's Strength of Materials.]

C. W. S.