upon the condition that he never part with it, being the first of the sort that ever was made, invented by my late uncle, John Hadley, Esq., and made under the direction and with the assistance of his two brothers, George and Henry.'
[A Biographical Account of John Hadley, Esq., V.P.R.S. … and his brothers George and Henry (anonymous, a copy is in Trinity College Library, Cambridge); Phil. Trans. ut supra and xl. 154, xlii. 243; Dalton's Meteorolog. Observations, ut supra; Cass's Hist. East Barnet, pp. 74, 80.]
HADLEY, GEORGE (d. 1798), orientalist, was appointed a cadet in the East India Company's service in 1763, and gained his first commission on the Bengal establishment on 19 June of that year. He became lieutenant on 5 Feb. 1764, and captain on 26 July 1760, and retired from the service on 4 Dec. 1771 (Dodwell and Miles, Indian Army List, 1760-1834, pp. 124-5). Finding it impossible to properly discharge his duty as a commander of a company of sepoys without a knowledge of their language, Hadley reduced their dialect to a grammatical system in 1765. A copy of his manuscript grammar fell into the hands of a London publisher; it was printed very incorrectly in 1770, and was circulated in Bengal. Hadley thereupon published a correct edition, entitled 'Grammatical Remarks on the practical and vulgar Dialect of the Indostan Language commonly called Moors. With a Vocabulary, English and Moors,' 8vo, London, 1772; 4th edit., enlarged, 1796. He published also 'Introductory Grammatical Remarks on the Persian Language. With a Vocabulary, English and Persian,' 4to, Bath, 1776. Hadley died on 10 Sept. 1798 in Gloucester Street, Queen Square, London (Gent. Mag. 1798, pt. ii. p. 816). In 1788 Thomas Briggs, a printer, of Kingston-upon-Hull, persuaded Hadley to put his name to a wretched compilation called 'A New and Complete History of the Town and County of the Town of Kingston-upon-Hull,' 4to.
[Hadley's Prefaces; Brit. Mus. Cat.]
HADLEY, JOHN (1682–1744), mathematician and scientific mechanist, born on 16 April 1682, was the son of George Hadley, deputy-lieutenant and afterwards, in 1691, high sheriff of Hertfordshire; his mother was Katherine FitzJames. He must be distinguished from an older John Hadley who was also skilled in practical mechanics. Desaguliers, when describing the waterworks put up at London Bridge, near the beginning of the eighteenth century, says that 'the contrivance for raising and falling the waterwheel was the invention of Mr. Hadley, who put up the first of that kind at Worcester, and for which a patent was granted him' in 1693 (Desaguliers, Lectures, ii. 528). On 21 March 1717 the younger Hadley became a fellow of the Royal Society. On 1 May in the following year he drew up a report on an abstruse mathematical question, which had been proposed apparently by Maclaurin, with the conclusion 'that the writer had shown the formation of several trajectories in which bodies might move about a gravitating centre, the gravitating power being as any dignity of the distance, either integer or fracted.' This is evidence of Hadley's knowledge of advanced mathematics, which is confirmed by an analysis which he drew up of Bianchini's work on the planet Venus (Phil. Trans. xxxvi. 158).
In 1719-20 Hadley obtained his first great success by the improvement he effected in the reflecting telescope, which had been left imperfect by both Newton and Gregory, and thus produced the first instrument of that kind which had sufficient size and accuracy to be of service to astronomers. His first large reflector was shown on 12 Jan. 1721 to the Royal Society, who 'ordered their hearty thanks to be recorded,' and state in their journals that 'the force [of the telescope] was such as to enlarge an object near two hundred times, though the length thereof scarcely exceeds six feet.' The reflecting metallic mirror was about six inches in diameter, with a focal length of over five feet two inches. Dr. Bradley reported that with it he had seen 'the transits of Jupiter's satellites and their shadows over the disc, the black list in Saturn's ring, and the edge of the shadow of Saturn cast on the ring … also several times the five satellites of Saturn.' Hadley's new telescope was praised in equally high terms by Dr. Halley, the astronomer royal, who tested it 'on the bodies and satellites of the superior planets,' and on 6 April in the same year Hadley communicated a series of observations which he himself had made on the transit of Jupiter's satellites, &c. (ib. xxxii. 384).
Hadley's success with his first reflector and a second equally large led him to effect great improvements in the Gregorian telescope. His friend Dr. Bradley also acquired a taste for constructing these instruments, and the result of their efforts was that reflecting telescopes speedily came into general use, and have since been supplied regularly by opticians (Brewster, Life of Newton, i. 55).
From 1726 till his death Hadley was annually elected member of the council of the Royal Society, and on 12 Feb. 1728 he was sworn into the office of vice-president.
