References.—Harris, “Rud. Electricity,” 1853, p. 93, and his “Frictional Electricity,” 1867, p. 23; “The Electrical Researches of the Hon. Hy. Cavendish,” Cambridge, 1879, Nos. 559, 568, 569, 580; Thos. Young, “Nat. Phil.” passim; Phil. Trans., Vol. LXIV. pp. 133, 389; Vol. LXVI. p. 513; Vol. LXVII. pp. 1, 85; also Hutton’s abridgments, Vol. XIII. pp. 323 (new electrometer), 512, 551, 659; Vol. XIV. pp. 90, 97, 130, 473; Transactions of the Humane Society, Vol. I. p. 63; Ronayne and Henley, “Account of Some Observations ...” London, 1772 (Phil. Trans., p. 137).
A.D. 1772.—Cavendish (Henry), F.R.S., eldest son of Lord Charles Cavendish, and a prominent English scientist, sometime called “The Newton of Chemistry” (“the most severe and cautious of all philosophers”—Farrar, 284), commences investigating the phenomena of electricity, the results of which study were duly communicated to the Philosophical Transactions. His papers embrace twenty-seven mathematical propositions upon the action of the electric fluid, and contain the first distinct statement of the difference between common and animal electricity.
Cavendish made many very important experiments upon the relative conducting power of different substances. He found that a solution of one part of salt in one part of water conducts a hundred times better, and that a saturated solution of sea-salt conducts seven hundred and twenty times better than fresh water, also that electricity experiences as much resistance in passing through a column of water one inch long as it does in passing through an iron wire of the same diameter four hundred million inches long, whence he concludes that rain or distilled water conducts four hundred million times less than iron wire.
He decomposed atmospheric air by means of the electric spark, and he successfully demonstrated the formation of nitric acid by exploding a combination of seven measures of oxygen with three of nitrogen. The latter he did on the 6th of December, 1787, with the assistance of Mr. George Gilpin, in presence of the English Royal Society. (For George Gilpin, consult “Bibl. Britan.,” Vol. XXXVI, 1807, p. 3; Phil. Trans. for 1806.)
He improved upon Priestley’s experiments after studying thoroughly the power of electricity as a chemical agent. In one of his experiments he fired as many as five hundred thousand measures of hydrogen with about two and a half times that quantity of atmospheric air, and having by this means obtained 135 grains of pure water, he was led to the conclusion which Mr. Watt had previously maintained, that water is composed of two gases, viz. oxygen and hydrogen.
He explains why no spark is given by the electrical fishes: the latter may contain sufficient electricity to give a shock without being able to make it traverse the space of air necessary for the production of a spark, as the distance through which the spark flies is inversely (or rather in a greater proportion) as the square root of the number of jars in operation.
For an account of his experiments anticipating Faraday’s discovery of the specific inductive capacity of various substances, see Chap. XI. pp. 69–142 of Gordon’s “Physical Treatise,” etc., London, 1883. See, likewise, J. Clerk Maxwell’s “Electrical Researches,” etc., Cambridge, 1879, pp. liii-lvi, as well as references therein made, more particularly at articles Nos. 355–366, 376; also the notes 27, 29 as per Index at pp. 450 and 453; Phil. Trans., Vol. CLXVII (1877), p. 599; Sparks’ edition of Franklin’s “Works,” Vol. V. p. 201.
References.—Dr. G. Wilson’s “Life and Works of Hon. Henry Cavendish,” London, 1851; Sturgeon’s Annals, Vol. VI. pp. 137, 173, etc.; Noad, “Manual,” etc., pp. 14, 161; Harris, “Electricity,” pp. 136, 140; Harris, “Frictional Electricity,” pp. 23 and 45; Whewell, “Hist. of the Ind. Sciences,” 1859, Vol. II. pp. 203–206, 273–275, 278; C. R. Weld, “Hist. Roy. Soc.,” for Lord Charles Cavendish, Vol. II. pp. 171, 176–185, 221; T. E. Thorpe, “Essays in Historical Chemistry,” London, 1894, pp. 70, 110; Thomas Thomson, “Hist. Roy. Soc.,” London, 1812, pp. 456, 457, 471; Sir William Thomson’s “Works,” 1872, pp. 34, 235; Phil. Trans. for 1776, Vol. LXVI. p. 196; Thos. Young, “Lectures,” 1807, Vol. I. pp. 658, 664, 751, and Vol. II. p. 418.
A.D. 1773.—Walsh (John), F.R.S., demonstrates the correctness of Dr. Bancroft’s opinion that the shock of the torpedo is of an electrical nature, resembling the discharge from a Leyden jar. In the letter announcing the fact, which he addressed to Franklin, then in London, he says: “He, who predicted and showed that electricity wings the formidable bolt of the atmosphere, will hear with attention that in the deep it speeds a humbler bolt, silent and invisible; he, who analyzed the electric phial, will hear with pleasure that its laws prevail in animated phials; he, who by reason became an electrician, will hear with reverence of an instructive electrician gifted at its birth with a wonderful apparatus, and with skill to use it.”
Mr. Walsh’s experiments were made off Leghorn, in company with Dr. Drummond, as stated in Phil. Trans., 1775, p. 1, and were confirmed by Johan Ingen-housz as well as by the Italian naturalist, Lazaro Spallanzani (at A.D. 1780). The last named found the torpedo shocks strongest when it lay upon glass, and that when the animal was dying the shocks were not given at intervals, but resembled a continual battery of small shocks: three hundred and sixteen of them have been felt in seven minutes.