# Dictionary of National Biography, 1885-1900/Kater, Henry

​KATER, HENRY (1777–1835), man of science, was born in Bristol on 16 April 1777. His father, Henry Kater, of German descent, was one of the firm of John & Henry Kater, sugar-bakers, Tucker Street (Bristol Directory, 1793–4). The younger Kater was placed by his father in a lawyer's office, where he remained two years, and picked up some legal knowledge, on which he valued himself in after life. On his father's death, in 1794, he resumed his favourite mathematical studies. On 25 April 1799 he became ensign by purchase in the 12th foot. He joined his regiment in Madras, and became lieutenant 3 Nov. 1803. He became assistant to William Lambton (1756–1823) [q. v.], then a middle-aged subaltern in the 33rd foot, who had been entrusted by the Madras government with the survey of the country between the Malabar and Coromandel coasts. Kater assisted in the measurement of a base-line near St. Thomas's Mount in 1802, in connection with the Bangalore base; in the subsequent triangulation for survey purposes, and in the measurement of an arc of the meridian (reported in Asiatic Researches, vol. viii.). The maps and reports are now in the map-room of the India office (Clements Markham, Indian Surveys). During this period he suggested an improved hygrometer (see Asiatic Researches, vol. ix.) He also devised an improved form of pendulum (see Nicholson's Journal, 1808, vol. xx.). Kater returned home on account of ill-health, and was promoted to a company without purchase in the 62nd foot on 13 Oct. 1808. He entered the senior department of the Royal Military College, Sandhurst, and after passing a distinguished examination, joined the 2nd battalion of his regiment in Jersey. He was ordered to Uxbridge on recruiting service, and was several years brigade-major at Ipswich, the headquarters of the eastern district. He was placed on permanent half-pay at the reductions of 1814. In 1815 he was elected a fellow of the Royal Society of London, of which he was long treasurer. The Emperor of Russia also conferred on him the order of St. Anne, in recognition of his services in the preparation of standard measures for the Russian government. He was employed in pendulum experiments at the chief stations of the trigonometrical survey of Great Britain, and in 1821–3 was associated with Arago, Mathieu, and Colby in the observations for determining the difference of longitude between the observatories of Greenwich and Paris. He reported upon them very fully in the ‘Philosophical Transactions,’ 1828. He lived chiefly in London, employed in scientific pursuits. Kater died at his residence, York House, Regent's Park, London, on 26 April, 1835. In 1827 he lost a daughter, aged 16, who had shown remarkable scientific promise.
Kater was a member of all the leading scientific societies at home and abroad. His most important contributions to science were reported in ‘Philosophical Transactions.’ While on the staff at Ipswich he made a series of experiments with the Cassegrainian and the Gregorian telescopes, leading to the conclusion that under equal conditions the illuminating power of the Cassegrainian was about double that of the Gregorian, the inferiority of the Gregorian being, he thought, due to the interference of rays after reaching the focus (Phil. Trans. 1813, pp. 206–12, and 1814). He devised an improved method of dividing astronomical circles on the principle of the beam-compass, and succeeded in measuring 1/10000 inch. He laboured for some years upon the exact determination of the length of a pendulum vibrating seconds. It became of practical importance upon the introduction of a bill for establishing a uniform system of weights and measures in the United Kingdom, the standard foot being determined by reference to such a pendulum. Kater solved the problem by the application of Huyghens's principle of the reciprocity of the centres of suspension and oscillation. The experimental determination of the length by this means, and the adoption of the ‘knife-edge’ principle of suspension, enabled Kater to produce a seconds pendulum of extraordinary delicacy (ib. 1818). His labours were rewarded by the Copley gold medal for 1817. At the request of the society Kater repeated his pendulum observations at the principal stations of the ordnance survey. With the aid of Clairaut's theorem he ​investigated the decrease of gravity from the equator to the poles, and the extraordinary sensitiveness of his pendulum suggested to him the possibility of discovering differences in the subjacent strata of a region by noting these minute variations in the force of gravity (ib. 1819). He delivered the Bakerian lecture for 1820 on the best kind of steel for compass-needles (ib. pp. 104–30), having arrived at very curious and unexpected results. He completed the investigations of Sir George Augustus William Schuckburgh Evelyn [q. v.] into the weights of a standard cube, cylinder, and sphere, by ascertaining their dimensions, in view of the approaching report of the commissioners of weights and measures. The apparatus employed by him for the purpose, and the results obtained, were reported by him very fully (ib. 1821, 1825, 1826). Perhaps the most important of Kater's contributions to science was the invention of the floating collimator, for determining the line of collimation of a telescope attached to an astronomical circle in any position of the instrument (ib. 1825, 1828). Other papers by him, many on astronomical subjects, will be found in different volumes of ‘Philosophical Transactions’ (1819, 1821, 1823, 1828, 1831, 1833), in the ‘Quarterly Journal of Science’ (1821 vol. xi., 1822 vol. xii.), in ‘Astronomische Nachrichten’ (1826, vol. iv. cols. 113–16), in ‘Astronomical Society's Memoirs’ (1831, iv. 383–9), and ‘Astronomical Society's Monthly’ (1831–3, ii. 178–80). In 1832 Kater published ‘An Account of the Standards prepared for the Russian Government,’ London, 4to; a copy of the work is in the library of the Royal Society. He helped to frame the admiralty instructions for the care of instruments in arctic expeditions; contributed some observations on specks in the eyes to Guthrie's work on ‘Cataract’ [see Guthrie, George James], and wrote the chapter on balances and pendulums in the volume ‘Mechanics’ of Lardner's ‘Cabinet Cyclopædia,’ London, 1830.
H. M. C.