(b. London, England, 3 April 1715; d. London, 10 May 1787), physics, botany, medicine
Watson, the son of a cornchandler, obtained a sound basic education at the Merchant Taylors’s school before apprenticing himself to an apothecary on 6 April 1731 for a term of eight years.1 Apothecaries were then enjoying new opportunities and obligations in consequence of having won in 1704, at the expense of their old enemies the physicians , the right to prescribe as well as to compound medicine. An apprentice accordingly had much to learn: botany, chemistry, drug, making, and the diagnosis and treatment of common complaints. Watson, “never indolent in the slightest degree” and an “exact economist of his time” (Pulteney, 334), mastered these subjects, especially chemistry and botany, in which he won the annual prize of the Apothecaries Society for skill in identifying plants in situ (Pulteney, 297). In June 1738, ten months short of the term of his apprenticeship, he purchased his freedom for two guineas and was sworn into the Apothecaries Society. The same year he married and set up in business for himself.
Through his botanical contacts Watson came to the Royal Society, of which he was to be one of the most productive adn influenced members. He first attended a meeting on 16 March 1738, as guest of John Martyn, Cambridge professor of botany in absentia, abridger of the Philosophical Transactions, and translator of Boerhaave.2 He was then patronized by Martyn’s friend Sir Hans Sloane, who with Martyn, Thomas Birch, and others signed Watson’s certificate for admission to the Society, which took place on 9 April 1741. His first communications to the Society dealt either with botany—for instance, an account of thepreviously undescribed star puffball (Geaster), which made him known to Continental authorities (Pulteney, 299)—or with medical oddities encountered in his practice. He continued to write on these matters, and what was more important, to keep his colleagues current with Continental advances in natural history. Among his later botanical papers are studies of the sex of plants, inventories of gardens, and descriptions of useful or poisonous plants. Among his reports those on platinum , on Linnaeus’ system, and on Peyssonel’s important but neglected demonstration of the animal origin of coral , were the most important (Pulteney, 298–309).
Although Watson’s natural history papers “do him credit, they would not of themselves have been sufficient to give him celebrity”3. His reputation came primarily from his studies of electricity, which he began, characteristically, by reproducing and transmitting a discovery made abroad. The discovery, the ignition of warmed spirits by an electric spark, apparently interested Watson as a chemical matter. He successfully extended the operation to all the inflammable liquids he had in stock,and showed that the minght be fired”repulsively,” the spark being drawn across the liquor in an electrified spoon rather than (as was customary) toward the contents of a grounded one [2, 481–487]. These and other small triumphs  brought Watson the Copley Medal for 1745 and a public that consumed four editions of his electrical papers  before any could be printed in the Philosphical Transactions4
Watson’s first important discovery, announced in October 1746 , was the failure of an expectation authorized by the commonly held effluvial theory of electricity. He anticipated—as did J. N. Allamand, G. M. Bose, and Franklin, all of whom tried the effect independently— that by insulating himself while rubbing a glass tube, he could generate more electricity than if he stood upon the floor and let the effluvia run to ground. Failure suggested to him, as it did to Franklin, that rubbing did not collect electrical matter from the galss, but raised it from the ground; in a word, the tubes and globes acted as “pumps” circulating the electrical “fire” That far Franklin and Watson went independently and together. In extending his system, however, Watson remained within the effluvial frame and did not attain the conception of contrary electrifications. For example, he observed that the usual arrangement, in which the electricity generated by a grounded operator rubbing the globe of an electrical machine runs on to an insulated iron bar, could be inverted by grounding the bar and insulating the operator . But he did not perceive that the bar and the man electrify oppositely, the first positively and second negatively (in Franklin’s terminology). Having missed this qualitative difference, Watson developed a crude electrical mechinics that assimilated the effluvia to a subtle, universal, springly “aether” The “pumps” disturb the equilibrium of this ether, which, in straining to regain its balance, brings about electrical attraction and repulsion, much as in the system of the abbé Nollet.
The Leyden jar ruined Watson’s theory as it did Nollet’s: Neither could account for the opposite electrifications, the condensing action, or the paradoxical role of glass.5 After an effete try [5, 64], Watson gave up explaining the jar [7, 102] and turned to examining its properties. He found, independently of Le Monnier and Daniel Gralath, that the shock could be increased by arming the bottle with lead6 or by thinning the glass [5, 31]; that the discharge passed in the most direct way through the conductors forming the external “circuit” [5,31]; that the discharge occurred in a time too short to measure ; and that it might travel great distances through the ground or across water.7
Watson’s second important electrical discovery was the work of Benjamin Franklin, whose first communication he reviewed before the Royal Society in January 1748 [7, 97–100]. This communication, which introduced the concepts of electrification plus and minus and likened the tube to a pump, may have owed something to Watson’s pamphlets of 1745 and 1746 [4, 5]; in any case Watson recommended it as paralleling ideas he himself had recently developed. John Bevis had found that if the operator A and another man B are insulated, A charges whenever B takes a spark from the revolving globe, but never (as Watson had discovered) without B’s intervention. B also charges, and A and B can exchange a bigger spark than either can with C, who stands on the ground. A similar experiment had taught Fanklin to ascribe to B a greater, and to A a less, than ordinary quantity of electrical matter; Watson concluded that A and B had ether at low and high density respectively, C in all cases being the standard. Although neither quantity of electrical matter not its density (a rough forerunner of potential) alone sufficed for an exact electrostatics, Franklin’s conception, which retained fewer effluvial trappings, was the more progressive. As it developed further from the common view in Franklin’s theory of the Leyden jar, Watson regarded it less favorably .
With the successful trial of Franklin’s theory of lightning at Marly in 1752, Watson ceased to be the innovating leader of English electricians and assumed instead the same roles in electrical studies that he held in botanical ones: promoter, umpire, reviewer, consultant, and minor contributor. He advertised the English confirmation of Marly, joined with Nollet in exposing the strange delusion of the medicated electrical tubes,8 abstracted foreign literature, advised on the construction of lightning rods,9 and reported his own competent experiments on discharge in racuo and medical electricity. He became an adherent of Franklin’s theory and a friend of’ its inventor, with whom he shared political views and an interest in technological innovation (Pulteney, 319–323).
Franklin’s success was not the only, or perhaps even the chief, cause of Watson’s withdrawal from independent electrical studies in the 1750’s. As his reputation rose, so did his sights, and the level and intensity of his medical practice. In September 1757 he received or bought an M.D. from the University of Halle;10 in December he asked to leave the Society of Apothecaries, which generously disfranchised him, for the large fee of £50, early in 1758. No doubt he sought his release to make himself more acceptable to the Royal College of Physicians, which licensed practitioners with foreign degrees but disdained local apothecaries, however qualified. In 1759 he became a licentiate, and three years later he was chosen physician to the Foundling Hospital.11 The next step, fellowship in the College, came slowly. The College elevated men without an Oxford or Cambridge M.D. only with great reluctance and after long probation. Watson allied himself with “rebel licentiates” led by John Fothergill, who tried to reform the statutes; but only minor concessions were made, and Watson did not attain the fellowship until 1784, and then speciali gratia.12 He subsequently held the office of censor in the College, and received a knighthood in 1786 in connection with his service. As a physician Watson was compassionate, generous, careful, and well-informed (Pulteney, 338). He interested himself chiefly in epidemic children’s diseases, which he saw at the Foundling Hospital, and wrote a useful pamphlet comparing methods of inoculating against smallpox .13
Watson was a leading member of several institutions. His steady service to the Royal Society, of which he became vice-president under the regime of his friend Sir John Pringle, has been mentioned. He acted as a trustee of the British Museum and arranged its botanical garden (Pulteney, 310). He helped support Priestley’s experiments. He was a charter member of the Royal Society (dinner) Club, founded in 1743; a regular at the learned social gatherings at the home of one Watson, a grocer in the Strand;14 and a member of the Society of Collegiate (Licentiate) Physicians and of the Club of Honest Whigs.15 He was an able, conscientious, clubbable man, “and his exact observance of the duties of social politeness must ever be remembered with pleasure by all those who enjoyed the happiness of his acquaintance” (Pulteney, 338).
1. Society of Apothecaries, Court Minute Books 8200/6, fol. 61v; Hartog, “Watson,” 956; and Pulteney, 296, wrongly begin the apprenticeship in 1730, probably on the strength of Watson’s attendance at school (1726-1730), for which see Register of Merchant Tovlors’ School, E. P. Hart, ed., II (London, 1936), 68. Presumably Watson delayed his apprenticeship until just after his sixteenth birthday and then bound himself for eight rather than for the more usual seven years to satisfy the apothecaries’ rule that the apprenticeship should not expire before the candidate reached twenty–four.
2. Royal Society, Journal Book, XVI, 212; G. C. Gorham, Memoir of John Martyn…(London, 1830).
3. Thomas Thomson, History of the Royal Society (London, 1812), 434; see tributes from Musschenbroek and Volta in Pulteney, 313 n.
4. Cf. H. Baker to P. Doddridge, 24 Nov. 1747, in Doddridge, Correspondence and Diary, J. D. Humphreys, ed., V (London, 1831), 28.
5. J. L. Heilbron, “A propos de l’invitation de la bouteille de
Leyde,” in Revue d’histoire des sciences, 19 (1966), 133–142.
6. [5, §28]. Watson had this suggestion from John Bevis (see Dictionary of National Biography, II, 451–452).
7. [5, §28]. This was a misapprehension, for in such cases each coating of the jar discharges separately to ground.
8. L. Trenngrove, “Chemistry at the Royal Society …II,” in Annals of Science, 20 (1964), 1–57.
9. . Watson was a member of the committee that advised the government on protecting the powder magazine at Purfleet. See D. W. Singer, “Sir John Pringle and His Circle. I,” in Annals of Science, 6 (1949), 127–180.
10. Pulteney, 326, which also credits Watson with a degree from Wittenberg; Clark, History…, 565 makes him a graduate of the medical school of the University of Edinburgh.
11. W. Munk, The Roll of the Royal College of Physicians of London, 2nd ed., II (London 1878), 348–349.
12. Clark, op. cit., 571–572; Fox, Dr. John Fothergill…, 143–151. See Watson to Fothergill, 16 Sept. 1771, in John Thomson, Account of the Life, Lectures and Writings of William Cullen, 2nd ed., I (Edinburgh-London, 1859), 657–660.
13. Charles Creighton. Epidemics in Britain, II (Cambridge, 1894), 500–503, 514, 705–706. Watson’s papers published in Fothergill’s compilation, Medical Observations and Inquiries, 6 vols. (London, 1757-1784), are noticed in Pulteney, 331–332. Also see Fox, op cit., 141–142.
14. A. Geikie, Annals of the Royal Society Club (London, 1917), 11, 141, 160; Singer, “Sir John Pringle,” 160.
15. Clark, op. cit., 565; Fox, op. cit., 317. See V. W. Crane, “The Club of Honest Whigs,” in William and Mary Quarterly, 23 (1966), 210–233.
I. Original Works. An adequate bibliography of Watson’s published work may be pieced together from Pulteney (see below) and from P. H. Maty, A General Index to the Philosophical Transactions [vols. 1–70] (London, 1787), 788–791. Neither mentions “An Account of Some of the More Rare English Plants Observed in Leicestershire,” in Philosophical Transactions of the Royal Society, 49 (1755-1756), 803–866; or Watson’s reviews of William Brownrigg’s The Art of Making Common Salt (1748), ibid., 45 (1748), 351–372, and of J. A. Braun’s De admirando frigore artificiale (1760), ibid., 52 (1761-1762), 156–172.
Among Watson’s important writings are  “De planta minus cognita, & hactenus non descripta,” ibid., 43 (1744-1745), 234–238;  “Experiments and Observations Tending to Illustrate the Nature and Properties of Electricity,” ibid., 481–501;  “Further Experiments and Observations” ibid., 44 (1746), 41–50;  Experiments and Observations Tending to Illustrate…, a reprinting of the two preceding works, which exists in two versions, one by J. Ilive (London 1745), and the other, differing by the addition of a preface, by C. Davis (London, 1746);  “A Sequel to the Experiments and Observations,” in Philosophical Transactions, 44 (1747), 704–749, preprinted as a pamphlet (London, 1746);  “A Collection of Electrical Experiments,” ibid., 45 (1748), 49–92;  “Some Further Enquiries…,” ibid., 93–120;  “An Account of Mr. Benjamin Franklin’s Treatise,” ibid.,47 (1751–1752), 202–210;  “An Account of a Manuscript Treatise…Intituled Traité du corail,” ibid., 445–469;  “Observations Upon the Effect of Lightning,” ibid., 52 (1764), 201–227; and  Art Account of a Series of Experiments Instituted With a View of Ascertaining the Most Successful Method of Inoculating the Smallpox (London, 1768).
MSS of Watson’s papers and reviews are preserved at the Royal Society and in the Sloane MSS at the British Museum; see A. H. Church, The Royal Society: Some Account of the “Letters and Papers” of the Period 1741-1806 (Oxford, 1908), 69; and A Catalogue of the Manuscripts Preserved in the British Museum, S. Ayscough, ed. (London, 1782). There are some fifty of Watson’s private letters in the British Museum, most among the Hardwicke Papers, for which see British Museum, Catalogue of Additions to Manuscripts …in the Years 1894-1899 (London, 1901). Watson’s large scientific correspondence, referred to by Pulteney and Wilson (see below), contained many formal reports intended for publication, the following being those that reached the Philosophical Transactions: 46 (1749-1750), 470; 47 (1751-1752), 553, 559; 48 (1753-1754), 153, 579, 786; 49 (1755-1756), 16, 371, 558, 579, 668; 50 (1757-1758), 240, 506; 52 (1761-1762), 40, 302; 58 (1768), 58, 136; 59 (1769), 23, 81, 241; 60 (1770), 233; 61 (1771), 136; 62 (1772), 54, 265, 469; 63 (1773), 1, 79.
There is a portrait of Watson at the Royal Society, reproduced in A. Geikie, Annals of the Royal Society Club (London, 1917), opp. 24.
II. Secondary Literature. For biographical data see R. Pulteney, Sketches of the Progress of Botany in England, II (London, 1790), 295–340, abstracted in H. B. Wilson, The History of Merchant Taylors’ School, II (London, 1814), passim; P. J. Hartog, “Watson, Sir William,” in Dictionary of National Biography, XX, 956–958; Society of Apothecaries, Court Minute Books, Guildhall Library MSS, vol. 8200/6, f. 61v, 138v; vol. 8200/7, f. 123v, 125v (information supplied by A. E. J. Hollaender, Keeper of MSS); George Clark, A History of the Royal College of Physicians, II (Oxford, 1966), 471, 476–479, 552–573, 586; H. C. Cameron et al., A History of the Worshipful Society of Apothecaries of London, I (London, 1963), 78–82, 132–135; and R, H. Fox, Dr, John Fothergill and His Friends (London, 1919), 141–151, 215, 317. For Watson’s botany see Pulteney. For his electricity see J. Priestley, The History and Present State of Electricity, 3rd ed., I (London, 1775), 97–101, 111–118, 130–145, 347–352; I. B. Cohen, Frankin and Newton (Philadephia, 1956), 390–413, 441–452, 501–505; and M. Gliozzi, “Studio comparativo delle teorie elettriche del Nollet, del Watson e del Franklin,” in Archeion, 15 (1933), 202–215.
J. L. Heilbron