TELEGRAPH (from Gk. tole, afar ± packu, graphei-n, to write). The transmission of messages by means of electricity. With the discovery that electric currents could be trans mitted instantly over long distances came the idea of employing them for signaling, and in 1774 Bishop Watson made sonic experiments in dis charging Leyden jars through 10.600 feet of wire, suspended on wooden poles, in the neighborhood of London. In the Scots Magazine in 1753 a detailed description of a plan for electric telegraphy is given, and in 1774 a telegraphic line was erected by Lesage at Geneva, Switzerland, which consisted of twenty-four wires connected to pith-ball electroscopes (q.v.), each represent ing a letter. When the connection between the frictional machine or charged conductor and any electroscope was made the pith-ball was repelled. The difficulty of using frictional machines, the only method for producing electricity then known, however, prevented the attainment of any prac tical results in this direction before the discovery of the voltaic cell. In Germany the invention of the telegraph is credited to S3mmering of Munich, whose original apparatus, constructed about 1809. was exhibited in operation at the Congress of Electricians at Frankfort in 1891. This instrument consisted of a series of volta meters each corresponding to a certain letter or signal. On closing the key in any circuit the signal was transmitted to the corresponding voltameters and the water in the appropriate tube was decomposed. A similar plan was pro posed about the same time by Dr. J. R. Coxe, of Philadelphia. Immediately after the discovery of electro-magnetism by Oersted, in 1820, Ampere determined to apply the idea to telegraphy, and read a paper before the Paris Academy of Sci ences on the use of coils of wire surrounding magnetic needles instead of voltameters for this purpose. Baron Schilling in 1832 exhibited a telegraphic model in Russia in which the letters were represented by the defleetions of a single needle. Weber and Gauss modified this plan by using a' magnet suspended horizontally, to which a mirror was attached. This arrangement enabled the passage of extremely weak currents to be ob served as a beam of light from a lamp was re flected from the mirror mounted in connection with the suspended needle and produced a bright spot which moved along a screen with any deflection of the needle under the in fluenee of the current. The idea was sub sequently employed by Thomson in the reflecting galvanometer. Steinheil of :Munich was the first to notice the important fact that by using the earth as a conductor no return wire was needed. He also invented a code of using but two ele mentary signals in different combinations, and an instrument for recording the characters on a moving strip of paper in the shape of two rows of dots. In America the invention of the tele graph is generally attributed to S. F. B. Morse (q.v.), though the principles on which it is based were first discovered by Joseph Henry (q.v.), who, however, failed to make any practi cal application of his discoveries. The electro magnet on which the action of the telegraph de pends was devised by Sturgeon of England and consisted of a piece of iron of horseshoe form surrounded by coils of wire. Henry, however, was the first to construct eleetro-magnets in a useful form, so that they were able to sustain considerable weights and to produce this magnet ic effect by the action of a distant battery. In the Albany Academy in 1832 he had a mile of wire strung, through which he passed a current which flowing through an electric magnet caused it to attract an armature and strike a bell, thus giving an audible signal. In 1835 at Princeton,
where he became professor, he used one circuit with an electro-magnet to open and close another circuit containing a battery and powerful mag net. He also had a wire stretched across the campus through which he transmitted the cur rent, using the ground for a return. In 1832 Morse first conceived his idea of the tele graph, and for a number of years was en gaged in bringing the invention to a successful outcome, it being publicly shown in 1837 in New York and other cities. In the development of the invention Morse was assisted by Alfred Vail, who was a partner in the enterprise and sup plied much of the mechanical skill necessary for the construction of the apparatus, as as capital, and many of the most important features are due entirely to his ingenuity. The telegraph was established as a commercial enterprise in Germany with Steinheil's system, in America with Morse's, and in England with Wheatstone and Cooke's. The first telegraph line in commercial operation was between Paddington and Drayton, in Eng land. in 1837, and was thirteen miles in length. This antedated by about seven years the Morse line, which was constructed between Washington and Baltimore and successfully inaugurated in 1844. The printing telegraph was first sug gested by Vail, in 1837, and in 1841 Wheatstone made an instrument for this purpose, though in neither case did the invention come into ex tended use. The Wheatstone apparatus did not work well, except through comparatively short distances, and at a very low rate of speed, being altogether inferior to the Morse telegraph. The superior efficiency of the latter in working direct through long distances was caused by the application of the relay and local circuit. In October, 1851, a convention of deputies from Austria, Prussia, Bavaria, Wiirttemberg, and Saxony met at Vienna to decide upon a common and uniform telegraph system. By this conven tion it was decided that the Morse system was practically the best, and it was therefore adopted, and at the present time this Morse system, or a modification of it, is in general use throughout the world.
In the Morse system the temporary magnetic attraction produced when a current of electricity sent along the wire is passed through a coil was used to impart a slight movement to a lever placed near the magnet, thereby giving a visible indication each time the current was sent through the wire at the distant station. Different combinations of current, each impulse being of momentary duration, were arranged to represent the letters of the alphabet, and by this means messages were spelled out over the wire from Washington to Baltimore. This is the founda tion of all electric telegraphs, though the appli cation of the principle is modified in innumerable ways, for the purpose of permitting the trans mission and the reception of messages to be done in various methods that are convenient for special places and uses. The numerous instru ments so employed may be classed under two heads—namely, those which record the signals so that they may he read at any time after the message is received, and those which give only a passing signal, indicated by a sound or a motion, and which, therefore, require the constant attention of a receiving operator. Among the former are several kinds—namely, those giving a record in arbitrary signs—i.e. in the dots and dashes of the Morse alphabet; those which print the message in ordinary type, such as the modern type-printing instrument, and lastly, a class of instruments giving a facsimile of the message, which, however, are not much used. See TELAU TOGRAPH.