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BEVIS or BEVANS, JOHN, M.D. (1693–1771), astronomer, was born 31 Oct. 1693, at Tenby, Pembrokeshire. His parents occupied a good position, and having been entered at Christ Church, Oxford, he took the degrees of B.A. and M.A. respectively 13 Oct. 1715 and 20 June 1718. He studied medicine as a profession, but Newton's 'Optics' was his inseparable companion, and he rapidly became a proficient in astronomy and optics. On the termination of his university career he travelled for some time in France and Italy, then settled in London as a physician some time before 1730. He was successful, but unsatisfied, until in 1738 he removed to Stoke Newington, where he had built and fitted up an observatory. Here he worked with such diligence, frequently taking 160 star-transits in a single night, that in 1745 he found himself in a position to undertake the compilation of a 'Uranographia Britannica,' or exact view of the heavens, in fifty-two large plates, including many more stars than had been given in Bayer's maps. An explanation accompanied each plate, and a catalogue of stars was added, with two hemispheres, representing the constellations according to the ancients. The work was all but ready for the press when, in 1750, John Neale, the publisher, became bankrupt; the plates, already completely engraved, were sequestered by the court of Chancery, as it proved, irrevocably; and Bevis's heavy toils remained without fruit.

His friendship for Halley, whom he assisted at Greenwich in observing the transit of Mercury, 31 Oct. 1736 (Phil. Trans. xlii. 622), led him to procure and superintend in 1749 the publication of his 'Tabulæ Astronomicæ' (an English version was issued in 1752), after they had been printed twenty years. He added some supplementary tables, with precepts for using the whole. In 1739 he ascertained by observation that the effects of aberration in right ascension corresponded no less accurately to Bradley's theory than those in declination; but in this Eustachio Manfredi had been, without his knowledge, nine years beforehand with him (Bradley, Miscellaneous Works, p. xxxiii). About the same time he drew up and communicated to Thomas Simpson a set of 'Practical Rules for finding the Aberration of the Fixt Stars,' published by him at page 11 of his 'Essays' (1740).

On 23 Dec. (O.S.) 1743 Bevis, ignorant as yet of its appearance elsewhere, discovered at London the great comet of 1744. 'Last night,' he wrote to Bradley, with whom he was in constant and confidential intercourse, 'about half an hour after seven, thought saw a comet, and afterwards found it to be one; the nucleus in the telescope seemed considerably bigger than Jupiter, with a large capillitium about it, though little of a tail; 'twas as easily seen as a star of the second magnitude' (ibid. p. 425). He also observed Halley's comet in May 1759 (Phil. Trans. li. 93). 'The transits of Venus of 6 June 1761 and 3 June 1769 were both observed by him, the former at Savile House, London, in company with Short and Bluir, the latter at Mr. Joshua Kirby's house at Kew, with a 3½-foot reflector, when he noticed certain curious effects of irradiation entirely unperceived by him in 1761. He was elected a fellow of the Royal Society 21 Nov. 1705, and acted as its foreign secretary from 11 Dec. 1700 to 13 Feb. 1772. A diploma bearing date 11 June 1750, and accompanied by a note from Maupertuis complimenting him on his 'inimitable Atlas' (then expected shortly to apptiar), constituted him a member of the Berlin Academy of Sciences; and he was chosen a correspondent of that of Paris 12 July 1768. Soon after the death of Bliss (2 Sept. 1764), being disappointed in his hopes of succeeding him as astronomer-royal, he took chambers in the Middle Temple, and resumed his long-suspended medical practice. Far, however, from abandoning astronomy, he fell a victim to his constancy in its cultivation. For in turning hastily from the telescope to the clock, while observing the sun's meridian altitude, he got a fall, from the effects of which he died, 6 Nov. 1771, aged 76. He was of a mild and benevolent disposition and lively temperament. His astronomical work appears to have been characterised by diligence rather than precision.

He published a work entitled 'Cymbalum Mundi;' a translation of a treatise by Professor H. Boerhaave, of Leyden, 'On the Venereal Disease and its Cure,' 1719; two pamphlets, the 'Satellite's Sliding Rule,' for determining the immersions and emersions of Jupiter's satellites, and 'An Experimental Inquiry concerning the Contents, Qualities, and Medicinal Virtues of the two Mineral Waters lately discovered at Bagnigge Wells, near London' (1760, 2nd enlarged edition 1767); besides twenty-seven short papers in the 'Philosophical Transactions' (vols. xl. to lix.), mostly records of his astronomical observations. He contributed to the few numbers published of the 'Mathematical Magazine,' and is said to have, from modesty, concealed his authorship of several creditable works. He cooperated in Dr. Watson's electrical experiment' in 1747 (Phil. Trans. xlv. 62, 77), suggested strengthening the charge of a Leyden jar by applying a coating of tinfoil (Priestley, Hist. of Electricity, p. 89), and first distinguished Dollond's lenses with the term 'achromatic'.

[Bernouilli's Recueil pour les Astronomes. ii. 331, 1772 (a French translation of a Biographical Account by J. Horsefall, F.R.S., Bevis's executor and friend); Rawlinson MSS., 4to. 6. 97, Bodleian Library; Hutton's Phil, and Math. Dict. i. 226, 1815; Poggendorff's Biog.-Lit. Handwörterbuch, 1863; Gent, Mag. xli. 523.]

A. M. C.