The name given to a machine, by which intelligence may be transmitted, with extraordinary rapidity, to great distances. There is reason to believe, that the principle of the modern invention of communicating information by means of signals, is of great antiquity. The moderns have, however, the merit of applying the principle, so as to render it a scientific, and almost perfect machine. Polybius described a very complete arrangement of signals by means of torches. The Marquess of Worcester, in his Century of Inventions, boasts of being able to do wonders in this way, as he was wont to do in others. Dr. Hook, whose genius as a mechanical inventor was perhaps never surpassed, delivered a "Discourse to the Royal Society, onthe21st of May, 1684, showing a way how to communicate one's mind at distances" of 30, 40, 100, and 120 miles, etc. "in as short a time almost as a man can write what he would have sent." In this discourse, which was published in Derham's Collections of his Experiments and Observations, the Doctor takes to his aid the then recent invention of the telescope, and explains all the details of the method by which characters exposed at one station, may be rendered plain and distinguishable at the others.
About sixteen years afterwards, Amontons proposed the construction of telegraphs in France; which much resembled Dr. Hook's. The method was as follows: -
Let there be people placed in several stations, at a certain distance from one another, that, by the help of a telescope, a man in one station may see a signal made in the next before him: he must immediately make the same signal, that it may be seen by persons in the station next after him, who are to communicate it to those in the following station, etc. These signals may be as letters of the alphabet, or as a cypher, understood only by the two persons who are in the distant places, and not by those who make the signals. The person in the second station making the signal to the person in the third, the very moment he sees it in the first, the news may be carried to the greatest distance in as little time as is necessary to make the signals in the first station. The distance of the several stations, which must be as few as possible, is measured by the reach of a telescope. Amontons tried this method in a small tract of land, before several persons of the highest rank, at the court of France. It was not, however, till the French revolution, that the telegraph was applied generally to useful purposes.
Whether M. Chappe, who is said to have invented the telegraph first used by the French, about the end of 1793, knew any thing of Amonton's invention or not, it is impossible to say; but his telegraph was constructed on principles nearly similar. The manner of using his telegraph was as follows: - At the first station, which was on the roof of the palace of the Louvre, at Paris, M. Chappe, the inventor, received in writing, from the Committee of Public Welfare, the words to be sent to Lisle, near which the French army at that time was. An upright post was erected on the Louvre, at the top of which were two transverse arms, movable in all directions by a single piece of mechanism, and with inconceivable rapidity. He invented a number of positions for these arms, which stood as signs for the letters of the alphabet; and these, for the greater celerity and simplicity, he reduced as much as possible. The grammarian will easily conceive that sixteen signs may amply supply all the letters of the alphabet, since some letters may be omitted, not only without detriment, but with advantage.
These signs, as they were arbitrary, could be changed every week; so that the sign of B, for one day, might be the sign of M, the next; and it wa3 only necessary that the persons at the extremities should know the key. The intermediate operators were only instructed generally in these sixteen signals; which were so distinct, so marked, so different, the one from the other, that they were easily remembered. The construction of the machine was such, that each signal was uniformly given in precisely the same manner at all times; it did not depend, on the operator's manual skill; and the position of the arm could never, for any one signal, be a degree higher, or a degree lower, - its movement being regulated mechanically. M. Chappe, having received at the Louvre the sentence to be conveyed, gave a known signal to the second station, which was Mont Martre, to prepare. At each station there was a watch-tower, where telescopes were fixed, and the person on watch gave the signal of preparation which he had received; and this communicated successively through all the line, which brought them all into a state of readiness.
The person at Mont Martre then received, letter by letter, the sentence from the Louvre, which he repeated with his own machine; and this was again repeated from the next height, with inconceivable rapidity, to the final station at Lisle. The first description of the telegraph was brought from Paris to Frankfort-on-the-Maine, by a former member of the Parliament of Bourdeaux, who had seen that which was erected on the mountain of Belville. As given by Dr. Hutton, it is as follows:a a is a beam or mast of wood, placed upright on a rising ground, which is about fifteen or sixteen feet high. b b is a beam or balance, moving upon the centre a a. This balance-beam may be placed vertically, or horizontally, or anyhow inclined, by means of strong cords, which are fixed to the wheel d, on the edge of which is a double groove, to receive the two cords. This balance is about eleven or twelve feet long, and nine inches broad, having at the ends two pieces of wood c c, which likewise turn upon angles, by means of four other cords that pass through the axis of the main balance - otherwise, the balance would derange the cords; the pieces C are each about three feet long, and may be placed either to the right or left, straight or square, with the balance-beam. By means of these three, the combination of movement is very extensive, remarkably simple, and easy to perform.