His experiments in firing gunpowder, hydrogen, etc., by the electric spark, are detailed at p. 78 of Priestley’s “History,” etc., London, 1775.
Watson was rewarded with the Copley medal for his researches in electricity, which brought him also honorary degrees from two German universities. He was knighted in 1786, one year before his death.
References.—“Watson’s Experiments and Observations on Electricity,” 1745, also his “Account of the Experiments made by some gentlemen of the Royal Society,” etc., 1748; Phil. Trans., Vol. XLIII. p. 481; Vol. XLIV. pp. 41, 388, 695, 704; Vol. XLV. pp. 49–120, 491–496; Vol. XLVI. p. 348; Vol. XLVII. pp. 202, 236, 362, 567; Vol. XLVIII. p. 765; Vol. LI. p. 394 (lyncurium of the ancients); Vol. LIII. p. 10; also the following abridgments: Hutton, Vol. IX. pp. 151, 195, 308, 368, 408, 410, 440, 553; Vol. X. pp. 12, 189, 197, 227, 233, 242, 303, 372–379, 525; Vol. XI. p. 419 (lyncurium of the ancients), 580, 660, 679; Vol. XII. p. 127; John Martyn, Vol. X. part ii. pp. 279–280, 290, 294, 329, 339, 347, 368, 407, 410. See likewise, Scientific American Supplement of Oct. 5, 1889, No. 718, pp. 11, 471, for an interesting engraving of Dr. Watson’s experiment made through the water of the Thames, as well as for a detailed account of Lemonnier’s experiment above referred to. For Mr. A. Trembley, consult Phil. Trans., Vol. XLIV. p. 58, and John Martyn’s abridgments, Vol. X. part ii. p. 321.
A.D. 1746.—Lemonnier (Pierre Claude Charles), a distinguished savant, who was member of the French Academy as adjunct geometrician before he had attained his twenty-first year and became foreign member of the English Royal Society three years later, was the first scientist who drew electricity from the narrow domain of the laboratory.
He confirmed the result previously obtained by Grey (A.D. 1720) that electric attraction is not proportioned to the mass or quantity of matter in bodies, but only to the extent of their surface, length having greater effect than breadth (Phil. Trans., Vol. XLIV for 1746, p. 290; Snow Harris, “Treatise on Frict. Elect.,” London, 1867, p. 239, and “Hist. de l’Acad.,” 1746). He found that an anvil weighing two hundred pounds gives but an inconsiderable spark, while the spark from a tin speaking-trumpet eight or nine feet long, but weighing only ten pounds, is almost equal to the shock of the Leyden phial. A solid ball of lead, four inches in diameter, gives a spark of the same force as that obtained from a thin piece of lead of like superficies bent in the form of a hoop. He took a thin and long piece of lead, and noticed that when it was electrified in its whole length it gave a very strong spark, but a very small one when it was rolled into a lump (Ac. Par., 1746, M. p. 369). It had likewise been shown by Le Roi and D’Arcy that a hollow sphere accepted the same charge when empty as when filled with mercury, which latter increased its weight sixtyfold; all proving the influence of surface as distinguished from that of mass (Tyndall, Notes on Lecture IV).
Lemonnier discovered that electricity is ever present in the atmosphere, that it daily increases in quantity from sunrise till about three or four o’clock in the afternoon, diminishing till the fall of dew, when it once more increases for a while, and finally diminishes again before midnight, when it becomes insensible. He observed a continual diminution of electricity as the rain began to fall, and he says: “When the wire was surrounded with drops of rain, it was observed that only some of them were electrical, which was remarkable by the conic figure they had; whilst the others remained round as before. It was also perceived that the electrical and non-electrical drops succeeded almost alternately; this made us call to mind a very singular phenomenon which happened some years before, to five peasants who were passing through a cornfield, near Frankfort upon the Oder, during a thunderstorm; when the lightning killed the first the third and the fifth of them, without injuring the second or the fourth” (Phil. Trans., Vol. XLVII. p. 550).
References.—Le Monnier, “Lois du Magnétisme,” Paris, 1776–1778; Phil. Trans., Vol. XLIV. p. 247; Vol. XLVIII. part i. p. 203; “Journal des Sçavans,” Vol. CXII for 1737, p. 73; also Hutton’s abridgments, Vol. IX. pp. 275, 308, 368, 591 (biogr.); John Martyn’s abridgments, Vol. X. part ii. pp. 329–348; “Philosophical Magazine,” Vol. VI. for 1800, p. 181, “Some Account of the Late P. C. Le Monnier,” 1715–1799; “Mémoires de l’Institut Nat. des Sc. et des Arts,” Hist. An. IX. p. 101; Mémoires de l’Acad. Royale des Sciences, 1746, pp. 14–24, 447, 671–696; 1752, Tome I. pp. 9–17, Tome II. 233–243, 346–362; 1770, p. 459; Bertholon, “Elec. du Corps Humain,” 1786, Vol. I. pp. 10–14; Harris, “Frict. Elec.,” p. 239; Sc. American Supplement, for Oct. 5, 1889, No. 718, pp. 11, 471. See also reports of the experiments of G. B. Beccaria, G. F. Gardini (“De inflexu,” etc., ss. 50, 51), Andrew Crosse and others at “Bibl. Britan. Sc. et Arts,” 1814, Vol. LVI. p. 524.
A.D. 1746.—Bevis (John), English astronomer and Secretary of the Royal Society, first suggested to Dr. Watson the external coating of the Leyden jar with tinfoil or sheet-lead, and was likewise the first to observe that the force of the charge increases as larger jars are employed, but not in proportion to the quantity of water they contain. As water only played the part of a conductor, he rightly thought that metal would do equally well, and he therefore filled three jars with leaden shot instead of with water. When the metallic connection was made it was found that the discharge from three jars was greater than that from two and the discharge from two much greater than that from one. This showed that the seat of the electric force is the surface of the metal and the glass, and proves that the force of the charge is in proportion to the quantity of coated surface.
Thus to Dr. Bevis belongs the credit of having constructed the first electric battery, although the honour has been claimed by the friends of Daniel Gralath (A.D. 1747).
References.—Phil. Trans., abridged, Vol. X. pp. 374, 377; Wilson, “Treatise,” London, 1752, Prop. XVII. p. 107.