FIG. 7.—CHAPPE'S AERIAL TELEGRAPH, 1793.
But the greatest improvement in aerial telegraphy was made during the French Revolution by Claude Chappe, a Frenchman living in Paris. In 1793, Chappe erected on the roof of the palace of the Louvre a post at the top of which was a cross-beam which moved on a pivot about the center like a scale beam (Fig. 7). The cross-beam could be moved horizontally, vertically or at almost any angle by means of cords. Chappe invented a number of positions for these arms and each position stood for a certain letter of the alphabet. Machines of this kind were erected on towers at places from nine to twelve miles apart and soon Chappe was sending messages from Paris to the city of Lille, 130 miles away. The messages were sent with great rapidity, for they passed from one tower to another with the velocity of light—about 185,000 miles a second—and it was possible for the operator to spell out about 100 words in an hour. And Chappe's messages could be sent at any time, day or night, for the arms of the machine were furnished with Argand lamps for night work.
Chappe's invention was the greatest which had thus far been made in the history of the message. The new system of telegraphy proved to be entirely successful and practical and it was not long before machines similar to those invented by Chappe were in use in England and other countries. In 1828, an English writer had the following words of praise for aerial telegraphy: "Telegraphs have now been brought to so great a degree of perfection that they carry information so speedily and distinctly and are so much simplified that they can be constructed and maintained at little expense. The advantages, too, which result from their use are almost inconceivable. Not to speak of the speed with which information is communicated and orders given in time of war, by means of these aerial signals the whole kingdom could be prepared in an instant to oppose an invading enemy."
FIG. 8.—STURGEON ELECTRO-MAGNET, 1825.
FIG. 9.—PROFESSOR HENRY'S ELECTRO-MAGNET, 1832.
But the aerial telegraph was soon to have a most dangerous rival. This rival was the electric telegraph. Many years before the invention of Chappe men had been experimenting with electricity with a view of sending messages by means of an electric current. These experiments began in 1728 when an Englishman named Gray caused electricity to produce motion in light bodies located at a distance of more than 600 feet. In 1748, the great Benjamin Franklin, who conducted so many wonderful experiments in electricity, sent an electric current through a wire which was stretched across the Schuylkill River and set fire to some alcohol which was at the opposite end of the wire. We may regard the flash of alcohol as a telegraph, for it could have been used as a signal. In 1819, Professor Oersted of Copenhagen brought a magnetic needle close to a body through which an electric current was passing and he observed that the needle had a tendency to place itself at right angles to the electrified body. In 1825, William Sturgeon of England coiled a copper wire around a bar of soft iron and found that when a current of electricity was sent through the wire the bar of iron became a temporary magnet; that is, the bar of iron attracted a needle when the current was passing through the wire and ceased to attract it when the current was broken (Fig. 8). These discoveries of Oersted and Sturgeon led to the invention known as the electro-magnet and the electro-magnet led rapidly to the invention of the electric telegraph, for by means of the electro-magnet a signal can be sent to a distance as far as a current of electricity can be sent along a wire. In 1831, Professor Joseph Henry, one of America's most distinguished scientists, discovered a method by which an electric current could be sent along a wire for a very great distance. The next year Henry constructed and operated an apparatus which was essentially an electric telegraph (Fig. 9). "I arranged," he said, "around one of the upper rooms of the Albany Academy a wire of more than a mile in length through which I was enabled to make signals by sounding a bell. The mechanical arrangement for effecting this object was simply a steel bar permanently magnetized, supported on a pivot and placed with its north end between the two arms of a horse-shoe magnet. When the latter was excited by the current the end of the bar thus placed was attracted by one arm of the horse-shoe and repelled by the other and was thus caused to move in a horizontal plane and its further extremity to strike a bell suitably adjusted." Thus by 1832 the electric current had been used for sending signals at a distance and the electric telegraph had been invented.
But the electric telegraph was still only a toy. How could it be made a practical machine? How could it be used for sending messages in a satisfactory manner? Inventors everywhere worked diligently to discover a satisfactory method of signaling and many ingenious systems were invented. As early as 1837 a telegraph line was established between Paddington, England and Drayton—a distance of 13 miles—and messages were sent over the wire. But the line failed to give satisfaction and its use was discontinued. The honor of inventing the first really practical and useful system of electrical telegraphy was at last won by an American, S. F. B. Morse, a painter and professor of literature in the University of the City of New York. In 1832 Morse began to think about a plan for recording signals sent by electricity and by 1837 he was about ready to take out a patent for making signals "by the mechanical force of electro-magnetic motion." Morse was a poor man and he lacked the means of conducting his experiments. He was fortunate, however, in making the acquaintance and gaining the confidence of Alfred Vail, a student of the University. Vail furnished the money for the experiments and assisted Morse in perfecting his system. Indeed some of the most original and valuable features of Morse's system were invented by young Vail and not by Morse. In the face of much discouragement and bad luck Morse and Vail worked patiently on together and by 1843 their invention was completed.
