TELEGRAPH. (See also SIGNALLING.) Before the Chris tian era the bounds of electrical knowledge were confined to two facts : the attracting properties of rubbed amber, and the magnetic attraction of the lodestone; but although these phenomena were noted by Homer in the 12th century B.C. and others in later years, no attempt was made to explain them until the i3th century A.D. In 1267 Roger Bacon published his theories on the polar at traction of the lodestone. Following upon this publication rumours appear to have been circulated in connection with "a certain sympathetic needle" with which it was possible to converse over long distances. The sympathetic telegraph was first described in print by Porta in 1558. It consisted of two needle-shaped pieces of steel, each mounted at the centre of a dial with letters equally spaced around the periphery. Having "magnetized both needles by the same lodestone" by rubbing, a movement of the needle of one instrument was supposed to cause a synchronous movement of the needle on the other instrument, and communication, it was thought, could thus be set up between two distant points. Two ex perimenters who may be said to have laid the foundation for scientific electrical research were Gilbert and Cabeo; in 1600 the former found that a large number of substances which he called "electrics" attracted light bodies when rubbed, and that a bar of steel heated and cooled while in the magnetic meridian acquired magnetic polarity, i.e., pointed north and south ; the latter went a step further when he described in 1629 his theory of elec trical repulsion in similarly electrified bodies. In 165o, von Guericke devised the first electrical machine, consisting of a sulphur ball which was revolved and rubbed with the hand. Newton in 1675 substituted a glass globe for the sulphur ball, and in 172o Gray and Wheeler discovered and tabulated the electrical conductivity of different bodies. No practical results were obtained, however, until the principle of the Leyden jar— the forerunner of the modern electrical condenser—was demon strated by Musschenbroeck in 1745. He found that the effect of a charged Leyden jar may be conveyed to a distance by means of a wire conductor. That same year Franklin in America corn municated to Collinson in England the results of his investigations in connection with electricity and its place in nature. A year later Watson in England demonstrated that an electric current can be transmitted through 10,600 ft. of wire, using the earth for the completion of the circuit.
letter of the alphabet. At the receiving end of each wire a light ball was to be suspended above a piece of paper marked with an alphabetical letter. As a charge was sent along a given wire the ball would attract the paper beneath it, and by observing the movements of the paper words could be spelt out. He further suggested that bells might be substituted for the papers, which could be struck in turn by the ball as a charge was sent along any desired wire. The idea was carried out by Le Sage in Geneva in 1774 and similar telegraph systems were also suggested by Betan court and Lomond in 1787. An important advance was made in the latter's instrument as only one wire conductor was employed, and an alphabet of motions; but he employed a return wire in stead of the ground to complete the circuit.