Mr. Bennet also invented the electrical doubler, designed to increase small quantities of electricity by continually doubling them until visible in sparks or until the common electrometer indicates their presence and quality (Phil. Trans. for 1787, p. 288). It consists of three plates of brass, illustrated and explained at Fig. 9, p. 20, Vol. I of Prescott’s “Electricity and the Electric Telegraph,” 1885 edition, wherein it is stated that in forty seconds the electricity can thus, by continual duplication, be augmented five hundred thousand times. (See, for doublers, C. B. Désormes and J. N. P. Hachette, in Annales de Chimie, Vol. XLIX for 1804; J. Read (Phil. Trans. for 1794, p. 266); Sir Francis Ronalds (Edin. “Phil. Journal,” Vol. IX. pp. 323–325).)
At p. 105 of his “Rudim. Magnetism,” Snow Harris mentions the fact that, in some of his experiments, Mr. Bennet employed a magnetic needle suspended by filaments of a spider’s web as a magnetometer. In this connection, it may be said that, in the Philosophical Transactions for 1792, the assertion is made that a fine, and weakly magnetic steel wire suspended from a spider’s thread of three inches in length will admit of being twisted around eighteen thousand times and yet continue to point accurately in the meridian, so little is the thread sensible of torsion (Young’s “Course of Lectures,” 1807, Vol. II. p. 445). The use of the spider’s line had, during the year 1775, been recommended as a substitute for wires by Gregorio Fontana, who, it is said, obtained threads as fine as the eight-thousandth part of a line. In a lecture delivered at Boston, Mass., during the year 1884, Prof. Wood alluded to spiders’ threads estimated to be one two-millionths of a hair in thickness.
References.—Bennet, “New Experiments on Electricity,” etc., Derby, 1789, and “A New Suspension of the Magnetic Needle,” etc., London, 1792; Introduction to “Electrical Researches,” by Lord Henry Cavendish; Sc. Am. Supplement, No. 647, pp. 10, 327; Noad, “Manual,” p. 27; Cavallo, “Nat. Phil.,” 1825, Vol. II. pp. 199, 216; Phil. Trans., Vol. LXXVII. pp. 26–31, 32–34, 288–296; also the abridgments by Hutton, Vol. XVI. pp. 173, 176, 282 and Vol. XVII. p. 142; Sc. American, Vol. LI. p. 19; Annales de Chimie, Vol. XLIX. p. 45; Ezekiel Walker, Phil. Mag. for 1813, Vol. XLI. p. 415 and Vol. XLII. pp. 161, 215, 217, 371, 476, 485; also Vol. XLIII. p. 364.
A.D. 1788.—Barthélémy (Jean Jacques), who, after completing his studies in a French seminary of Jesuits, succeeded Gros de Boze as keeper of the king’s cabinet of medals, publishes in four volumes, at Paris, the first edition of his “Voyage du Jeune Anacharsis.” In this well-known work, begun by him in 1757, and translated into English under the title “Travels of Anacharsis the Younger in Greece,” Barthélémy alludes to the possibility of telegraphing by means of clocks (pendules, not horloges), having hands similarly magnetized in conjunction with artificial magnets. These were “presumed to be so far improved that they could convey their directive power to a distance, thus, by the sympathetic movements of the hands or needles in connection with a dial alphabet, communications between distant friends could be carried on.”
Writing to Mme. du Deffand in 1772, he observes:
“It is said that with two timepieces the hands of which are magnetic, it is enough to move one of these hands to make the other take the same direction, so that by causing one to strike twelve the other will strike the same hour. Let us suppose that artificial magnets were improved to the point that their virtue could communicate itself from here to Paris; you have one of these timepieces, we another of them; instead of hours we find the letters of the alphabet on the dial. Every day at a certain hour we turn the hand, and M. Wiard [Mme. du Deffand’s secretary] puts together the letters and reads.... This idea pleases me immensely. It would soon be corrupted by applying it to spying in armies and in politics, but it would be very agreeable in commerce and in friendship.”
References.—“Correspondance inédite de Mad. Du Deffand,” Vol. II. p. 99; letter of J. MacGregor in Journal Society of Arts, May 20, 1859, pp. 472, 473.
A.D. 1789.—Adriaan Paets Van Troostwÿk and Jean Rodolphe Deimann, Dutch chemists, associated for the purpose of scientific research, complete the experiments of Lord Cavendish and announce, in the Journal de Physique, their discovery of the decomposition of water through the electric spark, which latter is conveyed by means of very fine gold wires. As is now well known, water is by this means resolved into its two elements of oxygen and hydrogen, both of which assume their gaseous form.
The electric machine they employed was a very powerful double-plate one, of the Teylerian mode of construction, causing the Leyden jar to discharge itself twenty-five times in fifteen revolutions.
References.—“Mém. de la Soc. de Phys. Exp. Rotterdam,” Tome VIII; Journal de Physique, Vol. XXXIII; Noad, “Manual,” p. 161; “Encyl. Brit.,” Vol. VIII, 1855, pp. 530, 565; “Biog. Universelle,” Vol. X. p. 282; De La Rive, “Electricity,” Vol. II. p. 443; Wm. Henry, “Elements of Experimental Chemistry,” London, 1823, Vol. I. pp. 251, 252; Delaunay’s “Manuel,” etc., 1809, pp. 180–183; “Verhandl. van het Genootsch te Rotterdam” (“Mém. de la Soc. de Phys. Exp. de Rotterdam”) Vol. VIII; Poggendorff, Vol. I. p. 1555; Dove, p. 243; G. Carradori (Brugnatelli’s Annali di chimica, Vol. I. p. 1); John Cuthbertson, “Beschreibung einer Elekt. ...” Leipzig, 1790.