Telegraphy

as generally understood, a method of sending words by means of an electric current. Beginning with the discovery of chemical electricity by the Italian Volta in 1774, steady progress was made toward the invention of a telegraphic system. Oersted's discovery of the influence of an electric circuit on the magnetic needle in 1820 and the invention of the electromagnet were important steps. A number of methods for electric signaling were devised, but they were regarded as scientific playthings. In 1752 Benjamin Franklin, for instance, succeeded in sending electrical shocks across the Schuylkill River. In 1831 Joseph Henry, later connected with the Smithsonian Institution at Washington, constructed a magnetic telegraph a mile long. He trained his wire around the walls of a room in the academy at Albany, New York, in which he taught.

It remained for F. S. B. Morse of the University of New York City, and his friends, March 4, 1844, to construct the first practical telegraph line. It extended from Washington to Baltimore. The first message was a sentiment. The second was an announcement that James K. Polk had been nominated for president by the Democratic convention then in session at Baltimore. In the same year Charles Wheat-stone of King's College, London, established local lines in London. His system is still in use. The instruments and the code devised by Morse are in use in the United States and Canada. What is known as the Continental Code prevails in Europe.

The essential parts of the telegraph are an electric circuit, a current, a sending instrument, and a receiving instrument. A line wire grounded at each end, and the earth form the circuit. The current is generated by an electric battery. The sender breaks the circuit by depressing and releasing a key. The same result might be attained by breaking the line wire and bringing the ends together and separating them with the hands. The receiving instrument is composed of an electro-magnet placed within a coil of the circuit wire, and an armature held away from the magnet by a slight spring. When the operator presses the key, he closes the circuit; the electric current passes instantly and magnetizes the core of the electro-magnet in the receiving office. The armature is attracted. When the operator releases the lever of his key the circuit is broken, the current ceases, the core of the electro-magnet loses its magnetism, and the armature is released with a click. By repeating the operation a succession of click is made, readily interpreted by the receiving operator. The operator reads, not by clicks, but by intervals between clicks. A short interval and a long interval, that is to say, a dot and a dash, constitute the letter "A"; a long interval and three short intervals, that is to say, a dash and three dots, make the letter "B," etc. By attaching a needle point to the armature of the receiving instrument, and allowing it to play on a traveling tape of paper, it may be made to trace long and short marks, that is to say, dashes and dots, corresponding to the intervals. Practical operators depend on the ear.

There are many adjuncts, such as local circuits set in operation by the main circuit, dynamos in place of a battery to create the current, devices for sending several telegrams at the same time and for sending telegrams in opposite directions at the same time, etc., but the essential features of a telegraph system are as described.

Telegraph lines spread rapidly over both continents. In 1852 the first fire-alarm telegraph in America was established in Boston. The first line through the Rocky Mountains was built in 1862. In 1903 there were 30,984 telegraph operators and dispatchers in the employ of United States railways. In 1909 the Western Union Telegraph Company controlled nearly a million and a half miles of wire and maintained 24,321 offices. In that year it transmitted about 70,000,000 messages. Its wires would reach five times to the moon. Its receipts were $30,000,000. According to estimates based on good authority, but already out of date, the number of telegrams sent annually in the world is placed at the enormous number of 600,000,000, about two millions per working day.

In European countries the telegraph lines are owned by the state and are operated as a part of the postal system.

The author of the book of Job wrote, "Canst thou send lightnings, that they may go, and say unto thee, 'Here we are.'" In the face of such figures, these words seem almost prophetic.

TELEGRAPHIC ALPHABET.

See Cable; Marconi; Morse; Magnet; Electricity; Wireless Telegraphy; Franklin; Lightning