In Ronalds’ afore-named work the phenomenon of retardation of signals in buried wires is clearly foreseen and described, although Zetzsche endeavours to combat this assertion at p. 38 of his “Geschichte der Elektrischen Telegraphie,” Berlin, 1867. Speaking of the apprehended difficulty of keeping the wire charged with electricity, Ronalds suggests that when not at work “the machine be still kept in gentle motion to supply the loss of electricity by default of insulation; which default, perhaps, could not be avoided, because (be the atmosphere ever so dry, and the glass insulators ever so perfect), conductors are, I believe, robbed of their electricity by the same three processes by which Sir Humphry Davy and Mr. Leslie say that bodies are robbed of their sensible heat, viz. by radiation, by conduction, and by the motion of the particles of air.” He also gives descriptions of an improved electrical machine (eighth “Britannica,” Vol. VIII. p. 536; Sci. Am. Supp., No. 647, p. 10326; Noad’s “Manual,” p. 69), of a new method of electrical insulation and of some experiments on Vesuvius (Quarterly Jour. of Sci., Vols. II. p. 249; XIV. pp. 332–334), of a new electrograph for registering the charge of atmospheric electricity, of a pendulum doubler (Edin. Phil. Jour., Vol. IX, 1823, pp. 323–325) and of an attempt to apply M. De Luc’s electric column to the measurement of time. His other contributions relative to the dry pile are to be found in the Phil. Mag., Vols. XLIII. p. 414, and XLV. p. 466.
References.—“Biog. Mem. of Sir Francis Ronalds, F.R.S.,” by Alfred J. Frost, in Ronalds’ “Catalogue”; “Mem. of Dist. Men of Science,” by William Walker; Ronalds’ “Corres. and Memoir.,” in 1848–1849, to 1853, to April 17, 1855, to June 5, 1856, to Sept. 2, 1862, and in 1866–1870; Ronalds’ “Walk Through ... Exh. of 1855”; Illustrated London News of April 30, 1870; eighth “Britannica,” Vol. VIII. pp. 622, 627, for Ronalds’ improved electrometers and his telegraph; Nature, London, Nov. 23, 1871, Vol. V. p. 59; Journal of the Telegraph, March 15, 1875, Vol. VIII. p. 82, reporting the inaugural address of Mr. Latimer Clark before the English Society of Tel. Engineers; Comptes Rendus for 1838, Vol. VII. pp. 593, etc.; Sci. Am. Supp., No. 384, pp. 6, 127; No. 547, p. 8735, and No. 659, p. 10521, for his Telegraph; “Bombay Mag. Observatory,” 1850; Fortschrift des Phys., Vol. III. p. 586, and Buys-Ballot “Meteor. Preisfrage,” 1847, for Ronalds’ apparatus to measure atmospheric electricity; Phil. Mag., Vols. XLIV. p. 442; XLV. p. 261; XLVI. p. 203; and third series, Vols. XXVIII for 1846; XXXI. p. 191; British Ass. Reports for 1845, 1846, and Reports concerning the Kew Observatory for 1845, 1850, 1852; Phil. Trans. for 1847, Moigno’s Le Cosmos, Vol. XIII; L. Von Forster, “All. Bauzeitung” for 1848, p. 238; Noad’s “Manual,” pp. 184, 185, 748; Knight’s “Mechanical Dictionary,” Vol. I. p. 708; Turnbull’s “Electro-magnetic Telegraph,” p. 22; Annals of Electricity, Vol. III. p. 449; “English Cyclop.” (Arts and Sci.), Vol. VIII. pp. 71, 72; Jour. Soc. Teleg. Eng., 1879, Part XV, xxxviii; Vol. VIII, first part, p. 361; Reply to Mr. W. F. Cooke’s pamphlet, “The Elec. Teleg.: Was it Invented by Prof. Wheatstone?” London, 1855; Du Moncel, Vol. III; “Telegraphic Tales,” 1880, p. 42; J. D. Reid, “The Telegraph in America,” 1887, p. 71; Ure’s “Dict. of Arts,” etc., London, 1878, Vol. II (Elect. Metal.), p. 230; T. P. Schaffner, “Tel. Man.,” 1859, pp. 147–156; Silliman, “Principles of Physics,” 1869, p. 617; “Edin. Phil. Journal,” 1823, Vol. IX. pp. 322, 395.
A.D. 1816.—Porret (Robert) (1783–1868) communicates to the Annals of Philosophy (Vol. VIII. p. 74) a paper “On Two Curious Galvanic Experiments” (Electrovection, Voltaic Endosmose, or Electro-chemical Filtration).
He observed that when water was placed in a diaphragm apparatus, one side of which was connected with the positive and the other side with the negative electrode of the battery, that a considerable portion of the liquid was transferred from the positive toward the negative side of the arrangement. It has since been found that the same result occurs in a minor degree when saline solutions are electrolyzed, and, generally, the greater the resistance which the liquid offers to electrolysis the greater is the amount which is thus mechanically carried over.... It appears from the researches of Wiedemann (Pogg., Ann., Vol. LXXXVII. p. 321), which have been confirmed by those of Quincke, that the amount of liquid transferred, cæteris paribus, is proportioned to the strength or intensity of the current; that it is independent of the thickness of the diaphragm by which the two portions of liquid are separated; and that when different solutions are employed, the amount transferred in each case, by currents of equal intensity, is directly proportional to the specific resistance of the liquid. Miller, from whom the above is taken, says that this transfer has been minutely studied by Quincke, and gives an account of the latter’s work extracted from the Ann. de Chimie, LXIII. p. 479. Brewster’s allusion to Porret and Wiedemann (eighth “Britannica,” Vol. VIII. p. 630) is followed by the statement that Mr. Graham considers ordinary endosmose as produced by the electricity of chemical action.
References.—Graham, Vol. II. p. 266; De la Rive’s “Electricity,” Chap. IV. pp. 424–443; “Roy. Soc. Cat. of Sci. Papers,” Vol. IV. pp. 987, 988; Wm. Henry, “Elem. of Exp. Chem.” 1823, Vol. I. p. 178; C. Matteucci, “Traité des Phénom. Elect. Phys.,” 1844, p. 262 for Porret and Becquerel; Sturgeon’s “Sc. Researches,” Bury, 1850, p. 544; Poggendorff, Vol. II. p. 503; “Bibl. Britan.,” Vol. III, N.S., 1816, p. 15 (Thomson’s “Annals” for July 1816).
A.D. 1817.—Mr. J. Connolly makes known through an English and French pamphlet, entitled “An Essay on Universal Telegraphic Communication,” the details of his portable telegraph.
As shown in the thirty-sixth volume of the Transactions of the Society of Arts and in the twenty-fourth volume of the “Penny Cyclopædia,” his apparatus consists merely of three square boards painted with simple devices, like triangles, crescents, etc., the colours on the one side being the reverse of those on the other. Each of the six figures thus obtained is capable of producing four different distinct signals, making in all twenty-four, by successively turning each side of the board downward. In experiments made at Chatham, boards only eighteen inches square were found to answer for a distance of two miles, with a telescope having a magnifying power of twenty-five; and Mr. Connolly had also, it is said, exhibited these signals between Gros-nez and Sarque, a distance of seventeen miles, with boards twelve feet square.
At pp. 205, 208, of the Transactions of the Society of Arts, 1818, Vol. XXXV, and at p. 98, Vol. XXXVI for 1819, will be found Mr. Connolly’s system of telegraphing by means of flags in manner different from that of Lieut.-Col. John Macdonald alluded to at Pasley, A.D. 1808.
A.D. 1817.—In the “Encycl. Brit.” article treating of the influence of magnetism on chemical action, it is said that M. Muschman, Professor of Chemistry in the University of Christiania, made experiments to ascertain the effect of the earth’s magnetism on the precipitation of silver.
Desirous of explaining the chemical theory of the tree of Diana (Arbor Dianæ, first observed by Leméry), “he took a tube like a siphon and poured mercury into it, which accordingly occupied the lower part of the two branches; above the mercury he poured a strong solution of nitrate of silver. He then placed the two branches of the siphon so that the plane passing through them was in the magnetic meridian, and after standing a few seconds the silver began to precipitate itself with its natural lustre; but it accumulated particularly in the northern branch of the siphon, while that which was less copiously precipitated in the other branch had a less brilliant lustre, and was mixed with the mercurial salt deposited from the solution.” Muschman and Prof. Hansteen, having repeated this experiment with the same result, concluded that the magnetism of the earth had an influence on the precipitation of silver from a solution of its nitrate, and Muschman inferred from the experiment the identity of galvanism and magnetism (eighth “Britannica,” Vol. XIV. p. 42).