And thus, remarks Pepper, a prominent fact has slept in obscurity from the time of Sulzer to the time of Galvani.
References.—Izarn, “Manuel,” Paris, 1804, p. 4; Sturgeon, Annals, Vol. VIII. p. 363; also note at p. 491 of Ronalds’ “Catalogue”; Mém. de l’Acad. de Berlin, “Théorie Générale du Plaisir”; also “Temple du Bonheur,” published at Bouillon (Pays Bas), 1769, Tome III. p. 124, this last-named work being alluded to in the Journal des Débats, 7 Vendémiaire, au X; Edm. Hoppe, “Geschichte,” 1884, p. 128; C. H. Wilkinson, “Elements of Galvanism,” Vol. I. p. 69, note; Albert’s “Amer. Ann. d. Artz,” Vol. II. Bremen, 1802.
A.D. 1762.—Ledru Comus, French Professor of Natural Philosophy, invents a mode of telegraphing which is described and fully illustrated in Vol. I of Guyot’s “Nouvelles Récréations Physiques et Mathématiques,” Paris, 1769; as well as at p. 278 of “Mémoires, Correspondance et Ouvrages Inédits de Diderot,” Paris, 1821, in one of the letters to Mlle. Voland dated July 28, 1762.
His apparatus consisted of two dials, each bearing upon it twenty-five letters of the alphabet, which were moved by the agency of magnets and of magnetized needles; but Auguste Guérout considers the contrivance to have been merely a speculative one, as will be seen by his article, reproduced from “La Lumière Electrique” of March 3, 1883, in No. 384 of the “Scientific American Supplement.”
References.—Journal de Physique for 1775, Vols. V and VI; for 1776, Vol. VII; and for 1778, Vol. I; “Scelta di Opuscoli,” Milano, 1776.
A.D. 1765.—Cigna (Giovanni Francesco), native of Mondovi, Italy, and nephew to the electrician Beccaria (A.D. 1753), became secretary to the society of savants who gave birth to the Royal Academy of Sciences at Turin, and whose Memoirs contain his work, “De novis quibusdam experimentis electricis,” 1765.
At pp. 31–65 of the above Memoirs is given a full account of Cigna’s many curious observations made with silk ribbons placed in various positions, and in contact with different surfaces, instead of with the silk stockings employed by Symmer (A.D. 1759). He thus supplies the main defect of Dufay’s theory (A.D. 1733) by proving that the two opposite electricities are produced simultaneously. On p. 47 of the same work will be found a report of Cigna’s experiment with ice to ascertain whether electric substances contain more electric matter than other bodies.
References.—Vol. III. p. 168 of Nollet’s “Letters,” for an account of his observations upon the electric attraction and repulsion between conducting substances immersed in oil; as well as Chap. II. s. 3., vol. i. of Van Swinden’s “Receuil,” etc., published at La Haye, 1784. Should also be consulted: Cigna’s “Memoirs on Electricity and Magnetism” in the “Miscellanea ... Taurinensia,” and the several communications made by him to Priestley, Lagrange and others in 1775 concerning Volta’s electrophorus; likewise “Memorie istorische ... di Gianfrancesco Cigna de Antonmaria Vassalli Eandi,” Torino, 1821.
A.D. 1766–1776.—Lambert (Johann Heinrich), a profound German mathematician, native of Upper Alsace, publishes in Vol. XXII of the “Reports of the Berlin Academy” two beautiful Memoirs upon the “Laws of Magnetic Force” and upon the “Curvature of the Magnetic Current,” both of which, according to Dr. Robison, would have done credit to Newton himself.
In the first Memoir, says Harris, the author endeavours to determine two very important laws; one relating to the change of force as depending upon the obliquity of its application, the other as referred to the distance. In the second Memoir the curves of the magnetic current are investigated by the action of the directive or polar force of a magnet upon a small needle. Lambert concludes that the effect of each particle of the magnet on each particle of the needle, and reciprocally, is as the absolute force or magnetic intensity of the particles directly, and as the squares of the distances inversely.