In his “Cours Elémentaire de Physique,” Musschenbroek describes one of the peculiar electrical machines then being constructed by the well-known London instrument maker, George Adams, and a cut of it can be seen at p. 353, Vol. I. of the translation made by Sigaud de la Fond at Paris during 1769. Another of Adams’ machines is described and illustrated at p. 126 of the French translation of Cavallo’s “Complete Treatise,” published at Paris in 1785.
The invention of the Leyden jar is claimed with equal pertinacity for Kleist, Musschenbroek and Cunæus. While it is necessarily conceded that Von Kleist first published his discovery, it cannot be denied that his explanation of it is so obscure as, for the time, to have been of no practical use to others. It is stated by Priestley: “Notwithstanding Mr. Kleist immediately communicated an account of this famous experiment (which indeed it is evident he has but imperfectly described) to Mr. Winckler, at Leipzig, Mr. Swiettiki, of Denmark, Mr. Kruger, of Halle, and to the professors of the Academy of Lignitz, as well as to Dr. Lieberkühn, of Berlin, above mentioned, they all returned him word that the experiment did not succeed with them. Mr. Gralath, of Dantzig, was the first with whom it answered; but this was not till after several fruitless trials, and after receiving further instructions from the inventor. The Abbé Nollet had information of this discovery, and, in consequence of it says, in a letter to Mr. Samuel Wolfe, of the Society of Dantzig, dated March 9, 1746, that the experiment at Leyden was upon principles similar to that made with a phial half full of water and a nail dipped in it; and that this discovery would have been called the Dantzig experiment if it had not happened to have got the name of that of Leyden.”
In the thirty-eighth volume of the Philosophical Transactions, No. 432, p. 297, is given an abstract of a letter (dated Utrecht, January 15, 1733, O. S.), from Petrus Van Musschenbroek, M.D., F.R.S., to Dr. J. T. Desaguliers, concerning experiments made on the Indian Magnetic Sand, chiefly gathered along the seashore in Persia. After detailing his many observations, Van Musschenbroek asks: “And, now, what can this sand be? Is it an imperfect magnet, or Subtile Powder of it, which, when it is grown up into a greater lump, makes the vulgar Loadstones? So I conjectured at first; but when I found by experience that common Loadstones, exposed to the fire, according to some of the methods above-mention’d, did rather lose of their force than gain, I alter’d my opinion; and now confess that I have not yet penetrated into the knowledge of the nature of this matter.”
References.—Dalibard, “Histoire Abrégée,” p. 33; Dantzig Memoirs, Vol. I. pp. 407, 409, 411; Johann Gottlob Kruger, “Dissert. de Elect.,” Helmstadt, 1756 (Poggendorff, I. p. 1323); Priestley, 1777, “The Hist. and Pres. State of Electricity,” pp. 82–84; Opuscoli Scelti, 4to, xviii, 55; Pierre Massuet, “Essais,” Leide, 1751; Musschenbroek’s “Epitome elementorum,” etc., 1726, “Tentamina Experimentorum Naturalium,” 1731, and his “Disertatio Physica experimentalis de Magnete,” as well as his “Elementa Physicæ,” 1734, and the “Introductio ad Philosophiam Naturalem,” 1762, the last-named two works being greatly amplified editions of the “Epitome.” For Musschenbroek—Musschenbrock—consult also Phil. Trans., Vol. XXXII. p. 370; Vol. XXXVII. pp. 357, 408, also the following abridgments: Baddam, 1745, Vol. VIII. p. 42; Reid and Gray, Vol. VI. p. 161 (Musschenbroek to Desaguliers); Hutton, Vol. VII. pp. 105, 647 (magnetic sand); Eames and Martyn, Vol. VI. part ii. p. 255; John Martyn, Vol. VIII. p. 737 (magnetic sand). For this magnetic sand, consult also Mr. Butterfield’s article in Phil. Trans. for 1698, p. 336 and in the abridgments of Hutton, Vol. IV. p. 310.
A.D. 1745.—Watson (William), M.D., F.R.S., an eminent English scientist, bears “the most distinguished name in this period of the history of electricity.” His first letters, treating of this science, are addressed to the Royal Society between March 28 and October 24, 1745, and, on the 6th of February and the 30th of October, 1746, he communicated other similar papers to the same Society, all which, like his subsequent treatises, are to be found in the Philosophical Transactions.
Dr. Watson, like most scientists at the time, made numerous experiments with the Leyden jar, and he was the first to observe the flash of light attending its discharge. He says: “When the phial is well electrified, and you apply your hand thereto, you see the fire flash from the outside of the glass wherever you touch it, and it crackles in your hand.” It is to him that we owe the double coating of the jar, as well as the plus and minus of electricity.
He also shows conclusively that glass globes and tubes do not possess in themselves the electrical power, but only serve “as the first movers or determiners of that power,” and he also proves that the electric fluid takes the shortest course, passing through the substance of the best medium of connection and not along its surface. This, he demonstrated by discharging a phial through a wire covered with a mixture of wax and resin.
In order to ascertain the velocity of the electric fluid from the Leyden phial and the distance at which it could be transmitted (John Wood, at A.D. 1726), Watson directed a series of experiments upon a very grand scale, with the assistance of Martin Folkes, President of the Royal Society, Lord Charles Cavendish, Dr. Bevis, Mr. Graham, Dr. Birch, Peter Daval and Messrs. Trembley, Ellicott, Robins and Short. On the 14th and 18th of July, 1747, they experimented upon a wire carrying the electricity from the Thames bank at Lambeth to the opposite bank at Westminster, across Westminster Bridge, and, on the 24th of July, at the New River, Stoke Newington, they sent a shock through 800 feet of water and 2000 feet of land, as well as through 2800 feet of land and 8000 feet of water. Other experiments followed on the 28th of July and the 5th of August, as well as on the 14th of August of the same year, proving the instantaneous transmission of the fluid; while a year later, August 5, 1748, additional observations were made, through 12,276 feet of wire, at Shooter’s Hill, showing again that the time occupied in the passage of the electricity was “altogether inappreciable.” Regarding these experiments, Prof. Musschenbroek wrote to Dr. Watson, “Magnificentissimis tuis experimentis superasti conatus omnium.”
Watson’s experiments were repeated, notably by Franklin, across the Schuylkill at Philadelphia, in 1748; by Deluc, across the Lake of Geneva, in 1749; and by Winckler, at Leipzig, in 1750. It is said that Lemonnier (A.D. 1746) produced shocks at Paris through 12,789 feet of wire and that Bétancourt (A.D. 1795) discharged electric jars through a distance of twenty-six miles.
To Dr. Watson is also due the first demonstration of the passage of electricity through a vacuum. Noad tells us that he caused the spark from his conductor to pass in the form of coruscations of a bright silver hue through an exhausted tube three feet in length, and he discharged a jar through a vacuum interval of ten inches in the form of “a mass of very bright embodied fire.” These demonstrations were repeated and varied by Canton, Smeaton and Wilson.