agit actuellement au-dessous de ma méchanique, c'est elle qui va m'enlever sans beaucoup d'efforts," p. 32. The work was, course, one of pure imagination.

of

Of the beginnings of electricity, copious references will be found to amber and jet and their attraction for straws, chaff, and light bodies. The first original work of any extent on the general subject is Book II, of Gilbert's De Magnete, 1600, which, though abounding in original experiments on electrical attraction, makes no mention whatever of electrical repulsion. It stands out as a singular fact in the history of electrical discovery that an experimenter of Gilbert's diligence and ability should have failed to detect the mutual action of similarly electrified bodies, the discovery of that capital effect being reserved for Cabeo, who carefully describes it on page 194 of his Philosophia Magnetica, 1629, the description being here reproduced.

Apropos of nomenclature, Robert Symmer recognized in his New Experiments and Observations, 1760, that “negative electricity is in reality a positive, active power," a remark which appears to be justified by the activity and energy of our contemporary electrons, or atoms of electricity, as well as by a number of other electrical phenomena.

The evolution of the Leyden jar may be studied in the works of Winkler, of Leipzig, and Musschenbroek, of Leyden, and notably in the letters which Franklin wrote to his friend Collinson, of London, 1747-49. It is sometimes stated that Franklin was the first to ignite gunpowder by means of the electric spark, and that he did so in June, 1751. This is an error, inasmuch as Dr. Watson describes, in his

Experiments and Observations, 1746, page 40, a method which he successfully employed for firing gunpowder. Watson's book was well known to Franklin.

The development of the electrical machine may be followed from the sulphur-ball of von Guericke to the glassglobe of Newton, the glass-cylinder of Andrew Gordon, the Benedictine, the plate-machine of Martin de Planta of Sus in Switzerland, 1755, and the double-cushion plate-machine of Sigaud de la Fond, 1756. It will be seen that Winkler, of Leipzig, substituted for the palm of the hand-which was the rubber of early times-a leather cushion, which Canton afterwards covered with an amalgam of tin and mercury, thereby greatly increasing the output of the machine.

Among Galvani's predecessors the first place belongs to the celebrated Dutch naturalist, Swammerdam, who describes in his Biblia Naturæ, page 839, experiments which he made. in 1658 in presence of his munificent patron the Grand Duke of Tuscany, and in which he obtained muscular contractions of frogs' legs by using a pair of silver and copper wires.

Analogous experiments were made in 1784, and published in 1786 by Cotugno, professor of anatomy in the University of Naples, to the effect that he felt a benumbing sensation in his hand while dissecting a mouse which had bitten one of his students; but it was not, however, until Galvani published in his De Viribus Electricitatis, 1791, an account of experiments which he began in 1786, that the subject of "animal electricity," as it was called, commenced to attract serious attention.

Among Volta's predecessors should be reckoned Sulzer,

the Swiss æsthetical writer who, in a paper which he sent to the Berlin Academy in 1760 entitled Theorie der Angenehmen und unangenehmen Empfindungen, and which was published in 1762, notes the peculiar taste produced when strips of lead and silver, lying one above and the other below the tongue, are momentarily brought into contact. See also Sulzer's Nouvelle Théorie des plaisirs, 1767, page 155.

Nor should Professor Robison, of Edinburgh, be forgotten, who, in 1793, constructed what he called a rouleau, and which was nothing else than an early form of an electric column, or "pile." "I had a number of pieces of zinc," wrote Robison to Richard Fowler, "made of the size of a shilling, and made them into a rouleau with as many shillings. If the side of the rouleau be applied to the tongue so that all the pieces are touched by it the irritation is very strong and disagreeable."10

In 1802, two years after the invention of the voltaic pile, Romagnosi, of Trent, just missed discovering the magnetic effect of the electric current. In his letter, which appeared in the "Gazetta," of Trent, August 3, 1802, he says that he connected one end of a silver chain to a battery; and having passed the other, terminating in a little knob, through a glass tube for the purpose of insulation, he brought the knob close to the extremity of an insulated compass-needle, when he noticed that the needle was attracted and, after contact, repelled.

Govi gives the letter textually in his paper, entitled: Romagnosi e l'Elettro-Magnetismo, 1869, remarking that the

10 Fowler: "Experiments and Observations," p. 173. See also Encyclop. Brit., 1860, Vol. i., p. 963.

attraction and repulsion said to have been observed by the experimenter, were electrostatic and not electromagnetic effects.

Mojon, an eminent professor of chemistry of Genoa, was also on the verge of an epoch-making discovery, when, in 1804, he placed steel needles for a period of twenty days in circuit with a battery of one hundred elements of the crownof-cups type, and observed that they were permanently magnetized when removed from the circuit. See Izarn, Manuel du Galvanisme, 1804; also Aldini, Essai théorique et expérimental sur le Galvanisme, 1804.

Both Romagnosi and Mojon, however, failed to follow up the pregnant experiments which they made, thus leaving the field clear for Oersted, of Copenhagen, to announce to the world the discovery of the magnetic effect of the electric current, which he did in his pamphlet of four quarto pages printed in 1820 under the title "Experimenta circa effectum conflictus electrici in acum magneticam," a copy of which is in the Library. This capital discovery of the Dutch philosopher led Arago in France and Davy in England to magnetize steel needles by inserting them in a coil of wire conveying a current. Sturgeon, in 1825, replaced the hard steel by soft iron, and was thus the first to make an electromagnet as we know it to-day. He also applied the term electromagnet to the apparatus itself, a term which was adopted at once.

The student of the mathematical theory of the electrical current and its dynamical effects will be glad to have at hand. Ampère's papers, 1820-25, which contain a masterly analysis of the phenomena; Ohm's "Galvanische Kette," 1827; and Green's "Essay on the application of mathematical analysis to

the theories of electricity and magnetism," printed at Nottingham in 1828. In the opinion of Mr. Clark, this Essay is "one of the most important works ever written on electricity." Copies of this (first) edition are extremely rare.

The older modes of transmitting signals by lanterns, flags, and semaphores, are fully described by the inventors of the various systems whose works are in the Library. An illustration of the scant encouragement which inventors frequently receive from people in high places will be found in the letter which Mr. Barrow wrote to Ronalds, and in which the representative of the British Government says: "Mr. Barrow presents his compliments to Mr. Ronalds and acquaints him with reference to his note of the 3rd inst. that telegraphs of any kind are wholly unnecessary; and that no other than the one in use will be adopted." Mr. Barrow must have forgotten when penning these lines how efficiently his mechanical telegraph worked when the result of the battle of Salamanca (July 22, 1812) was semaphored from Plymouth to London, on which occasion the message was interrupted by a fog after the transmission of the first two words, viz., "Wellington defeated." The remainder of the dispatch, "the French at Salamanca," reached the capital only on the following morning.

It must be stated that Ronalds was not the first to use static electricity in 1816 for the transmission of signals, for such a mode was suggested in the Scots Magazine, 1753, and carried out in 1774 by Lesage of Geneva. On page 273 of the present volume will be found a facsimile reproduction of a letter in which Ronalds refers to a proposal made in

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