electromagnetic telegraph

A signaling, writing, printing, or recording apparatus, in which the impulses proceed from a magnetic force developed by voltaic electricity. The principle is that a ma of soft iron is rendered temporarily magnetic by the pa age of a current of electricity through a surrounding coil of wire. It differs from the electric telegraph properly considered, and also specifically from the magneto-electric telegraph (q.v.). (See also list under TELEGRAPH.) The earlier electric telegraphs were all what their name implies, and not electro-magnetic. [ELECTRIC TELEGRAPH.J The pioneers in its discovery were Sommering, in 1808, and Prof. Coxe, of Pennsylvania, about the same year. Then followed Oersted, in 1820. In 1832 Prof. Morse began to devote his attention to the subject of telegraphy, and in that year, while on his pa age home from Europe, invented the form of telegraph since so well known as "Morse's." A short line worked on his plan was set up in 1835, though it was not until June 20, 1840, that he obtained his first patent. His first idea was to employ chemical agencies for recording the signals, but he subsequently abandoned this for an apparatus sin, as; expect, Xenophon, exist. ph = f. which simply marked on strips of paper the dots and dashes composing his alphabet. The paper itself is now generally dispensed with, and the sig nals read by sound-a practice which conduces to accuracy in transmi ion, as the ear is found le liable to mistake the duration and succe ion of sounds than the eye to read a series of marks on In 1840 Wheat stone, whose attention seems paper. to have been drawn to telegraphy about 1834, patented a dial instrument, on which, however, he afterward adopted several modifications.