Page:Dictionary of National Biography volume 60.djvu/52

 On 6 Sept. 1757 he was created doctor of physic of the university of Halle, and about the same time of Wittemberg; he had already been elected member of the Royal Academy of Madrid. After having been disfranchised from the Society of Apothecaries he began to practise as a physician, and after examination was admitted L.R.C.P. on 22 Dec. 1759. About this time he moved from Aldersgate Street to Lincoln's Inn Fields. In October 1762 he was chosen physician to the Foundling Hospital, and retained this office till his death. On 30 Sept. 1784 he was elected fellow of the Royal College of Physicians. He was censor of the college in 1785 and 1786, and was knighted on 6 Oct. in the latter year, being one of those deputed by the college to congratulate George III on his escape from assassination by Margaret Nicholson. He was also a trustee of the College of Physicians, and for some time vice-president of the Royal Society. He died in Lincoln's Inn Fields on 10 May 1787. ‘Watson,’ says Pulteney, ‘was a most exact œconomist of his time … up usually in summer at six or earlier;’ he was in speech ‘clear, forcible, and energetic,’ ‘a careful observer of men,’ and endowed with an extraordinary memory, being called by his friends ‘the living lexicon of botany;’ he was, as a physician, of particularly humane temper.

Watson had a large foreign correspondence with Jean André Peyssonel, Clairaut, Bose of Wittemberg, the Abbé Nollet, Bernard de Jussieu, and others. In 1748 he showed civility to the naturalist Peter Kalm (1715–1779), a pupil of Linnæus, and in 1761 to Dr. Peter Simon Pallas of St. Petersburg (July 1761 to April 1762).

Watson contributed his first papers on electricity to the Royal Society in the course of 1745 and February 1746 (Phil. Trans. xliii. 481, xliv. 41, 695), and published them separately under the title ‘Experiments … [on] the Nature … of Electricity’ in 1746, a second edition being published in the same year. He notices therein that although ice, as well as water, is an ‘electric’ or non-conductor, moist air conducts, and he explains thereby the failure of electrical experiments in wet weather. On 30 Oct. 1746 (loc. cit. xliv. 704) Watson read his ‘Sequel to the Experiments … [on] Electricity,’ also published separately in the same year; he shows therein by his own experiments and those of his friend John Bevis [q. v.] that the ‘stroke’ of the recently discovered Leyden jar was, cæteris paribus, proportional not to its size, but to the conducting surfaces of its coatings—a point to which he returned later (Phil. Trans. 1748, xlv. 102). He notices that the ‘electrical force always describes a circuit’ (loc. cit. p. 718), and propounds the theory that in an electrical machine the glass globes, &c., have not the electrical power in themselves, but only serve as ‘the first movers and determiners of that power.’ He agrees with the Abbé Nollet in regarding electricity as existing normally everywhere in a state of equilibrium, and regards the electrical machine as comparable to a pump which accumulates electricity on the bodies we term ‘electrified.’ Watson's theory, though less clearly formulated, is hardly distinguishable from that of Benjamin Franklin. In his next paper (read 21 Jan. 1748, loc. cit. xlv. 93) Watson elaborates this theory and defines it more closely, quoting at the same time from Franklin's famous first letter (dated 1 June 1747) on the subject to Peter Collinson [q. v.] During 1747 and 1748 Watson, in conjunction with Martin Folkes [q. v.], then president, and a number of other members of the Royal Society, along with Bevis, carried out a long series of experiments on ‘the velocity of electric matter’ across the Thames at Westminster Bridge, at Highbury, and at Shooter's Hill, Watson planning and directing all the operations. They found that no appreciable interval could be perceived between the completion of the circuit 12,276 feet long, uniting the two coatings of a Leyden jar, and the receipt of the shock by an observer in the middle of the circuit; they conceived that the velocity of electricity was ‘instantaneous.’ In 1751 Watson, then ‘the most interested and active person in the kingdom in everything relating to electricity’, took great trouble to demonstrate the fallacy of certain statements of Georg Matthias Bose (1710–1761) and Johann Heinrich Winkler (1703–1770). In February 1752 he gave an account of the experiments on the electrical discharge in vacuo, on which he had been occupied since 1747, which, together with those of Nollet, are the first on the subject. In experimental details he was helped by John Smeaton [q. v.] and by Lord Charles Cavendish. He gives an accurate account of the phenomena, finds that rarefied air conducts electricity, though not so well as metals, and compares the discharge to the aurora borealis. On 16 Dec. 1762 he read before the Royal Society the substance of a letter to Lord Anson, first lord of the admiralty, advocating the use of the lightning conductors of Franklin for the powder magazine then being constructed at Purfleet. The Royal Society was formally consulted in the matter, and a committee was appointed to consider it, consisting of Watson, Henry Cavendish [q. v.],