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 Administration, and between 1898 and 1903 edited for the Navy Records Society the Letters and Papers of Admiral Sir Thomas Byam Martin in three volumes. He died at his house at Chalfont St. Peter, near Uxbridge, 17 September 1912, and was buried at Eltham. By his wife, Julia Frances Delmé (died 1897), daughter of Vice-Admiral James Arthur Murray, and great-granddaughter of John, third Duke of Atholl, he had two sons and two daughters.

 HARCOURT, AUGUSTUS GEORGE VERNON (1834–1919), chemist, was the elder son of Admiral Frederick E. Vernon Harcourt by his wife, Marcia, sister of the first Lord Tollemache, and grandson of Edward (Vernon) Harcourt, archbishop of York [q.v.]. He was born in London 24 December 1834, and died at his house, St. Clair, near Ryde, Isle of Wight, 23 August 1919. He was educated on the old classical lines at Cheam and at Harrow, and in 1854 entered Balliol College, Oxford.

When (Sir) Benjamin Collins Brodie [q.v.], a pupil of Bunsen, came to Oxford as professor of chemistry in 1855, the Balliol laboratory was placed at his disposal, and Harcourt became first his pupil and then his assistant. In 1858 Brodie migrated to the chemical department of the new museum of the university, and took Harcourt—still an undergraduate—with him as lecture assistant. Under Brodie, at the new museum, Harcourt began his researches with the exact determination of the oxygen absorbed by the metals potassium and sodium. In 1859 he was elected Lee's reader in chemistry and a senior student of Christ Church; in 1864 he became a tutor of Christ Church, and held that position until 1902. Meanwhile he had begun researches on the rate of chemical change, which, in conjunction with those of M. P. E. Berthelot in France and those of C. M. Guldberg in Norway, were to establish on a quantitative basis Berthollet's law of mass action. In the interpretation of his results Harcourt was associated with William Esson, the Oxford mathematician. Most chemical changes take place with a rapidity too great to be followed in detail. Harcourt investigated several cases of slow change before he found one sufficiently simple to admit of mathematical discussion, and in which the amount of change during definite intervals of time could be accurately measured. Having found such a case Harcourt and Esson proved experimentally that the velocity of the change varied directly with the quantities of each of the reacting substances. In studying the effect of temperature on the rate of this reaction, they arrived at a zero of chemical action, viz. 272.6° C., which is in wonderful agreement with the absolute zero calculated from physical data.

In applied chemistry Harcourt was chiefly drawn to questions concerning the purification and testing of coal-gas, as he was appointed in 1872 one of the three metropolitan gas referees. One of his early researches on coal-gas was his attempt to purify the gas from sulphur compounds. His ‘sulphur test’ came into wide use, but its application on a large scale for the purification of coal-gas has only recently been carried out with success. Perhaps his most signal improvement in the testing of gas was the introduction of the Pentane lamp as the official standard of light in place of the variable spermaceti candle. Another very useful investigation which occupied much of his time between 1899 and 1911 related to the administration of chloroform as an anæsthetic. After much patient labour he devised an ‘inhaler’, which his medical colleagues recommended to the British Medical Association as ‘possessing the advantages of simplicity, exactness, and portability’.

Harcourt was elected a fellow of the Royal Society in 1863, and served on its council from 1878 to 1880. In conjunction with Esson, he published four memoirs in the Philosophical Transactions, the third of which was the Bakerian lecture for 1895. Admitted to the Chemical Society in 1859, he served as one of its secretaries for eight years, 1865–1873, and was elected president in 1895. As became the nephew of one of the founders of the British Association—the Rev. William Vernon Harcourt [q.v.]—he early took an interest in its meetings and made many contributions to the chemical section, of which he was president in 1875. A few years later he was elected one of the general secretaries of the Association, an office which he held for fourteen years with conspicuous tact.

Harcourt married in 1872 the Hon. Rachel Mary, daughter of Henry Austin Bruce, afterwards first Baron Aberdare [q.v.]. He had two sons and eight daughters. To his happy family life at 238