ELECTRICITY, a powerful physical agent which makes its resistance mani fest by attractions and repulsions, by producing light and heat, commotions, chemical decompositions and other phe nomena.
About 600 B. C. Thales dicovered that when amber was rubbed with silk it be came capable of attracting light bodies. The ancients seem to have known no more than this regarding electricity; nor for the first 16 centuries of the Christian era was much addition made to the solitary known fact in electricity.
In 1600, Gilbert, who was surgeon to Queen Elizabeth and to James I., pub lished a book, "De Magnete," in which for the first time the word "electric" was used in connection with science. He died in 1603. He regarded magnetism and electricity as two emanations of one fundamental force. He showed that not merely amber, but sulphur, glass, etc., are electries. Otto Guericke, of Magde burg, discovered that there was a repul sive as well as an attractive force in electricity, and about 1647 constructed the first electrical machine.
Newton, in 1675, observed signs of electrical excitement in a rubbed plate of glass. Hawkesbee, who wrote in 1709, also observed similar phenomena ; and Dufay, in the "Memoirs of the French Academy," between 1733 and 1737, gen eralized so far as to lay down the prin ciple that electrified bodies attract all those which are not so, and repel them as soon as they have become electric by the vicinity or contact of the electric body.
Dufay also discovered that a body elec trified by contact with a resinous sub stance repelled another electrified in a similar way, and attracted one which had been electrified by contact with glass.
He thence concluded that the electric ity derived from those two sources was of different kinds, and applied the names vitreous and resinous to them. Franklin attributed this difference to an excess or deficiency of the electric fluid, the former condition existing in elec trified glass and the latter in resins.
Otto Guericke had discovered that his sulphur globe, when rubbed in a dark place, emitted faint flashes of light, and shortly afterward it was noticed that a similar phenomenon occurred at the sur face of the mercury when the barometer was shaken—a fact which one of the celebrated mathematicians, Bernouilli, attempted to explain on the Cartesian system, but which was afterward cor rectly attributed by Hawkesbee to elec tric charges. Wall, in 1708, observed
the sparks produced from amber, and Hawkesbee noticed the sparks and "snap ping" under various modifications.
Dufay and Abbe Nollet were the first to draw sparks from the human body, an experiment which attracted great atten tion, and became a species of fashionable diversion at the time.
The discovery of the Leyden jar is at tributed to Cunmus of Leyden, in 1746, who, while handling a vessel containing water in communication with an elec trical machine, was surprised at receiv ing a severe shock. A similar event had happened the year previous to Von Kleinst, a German prelate.
In the 18th century the names of the principal contributors to the advance ment of electrical science are Newton, Hawkesbee, Dufay, Guericke, Cunus of Leyden (to whom we owe the Leyden jar), and Franklin, who, 1747, pointed out the circumstances on which the action of the Leyden jar depends. Monnier the younger discovered that the electricity which bodies can receive depends on their surface rather than their mass, and Franklin soon found that "the whole force of the bottle and power of giving a shock is in the glass itself"; he further, in 1750, suggested that electricity and lightning were identical in their nature, and in 1752 demonstrated this fact by means of his kite and key. About the same time D'Alibard and others in France erected a pointed rod 40 feet high at Marli, for the purpose of verifying Franklin's theory, which was found to give sparks on the passage of a thunder cloud. Similar experiments were re peated throughout Europe, and in 1753 Richman was instantly killed at St. Petersburg by a discharge from a rod of this kind.