Alexander's Electric Telegraph

Alexander's Electric Telegraph
A model to illustrate the nature and powers of this machine, was exhibited on Wednesday evening at the Society of Arts in Edinburgh. The model consists of a wooden chest about five feet long, three feet wide, three feet deep at the one end, and one foot at the other. The width and depth in this model are those which would probably be found suitable in a working machine; but it will be understood that the length of the machine may be a hundred or a thousand miles, and is limited to five feet in the model merely for convenience. Thirty copper wires ex-tend from end to end of the chest, and are kept apart from each other. At one end (which, for distinction's sake, we shall call the south end) they are fastened to a horizontal line of wooden keys, precisely similar to those of a piano forte; at the other, or north end, they terminate close to thirty small apertures equally distributed in six rows of five each, over a screen of three feet square which forms the end of the chest. Under these apertures on the outside, are painted in black paint upon a white ground, the twenty-six letters of the alphabet, with the necessary points, the colon, semicolon, and full point, and an asterisk to denote the termination of a word. The letters occupy spaces about an inch square. The wooden keys at the other end have also the letters of the alphabet painted on them in the usual order. The wires serve merely for communication, and we shall now describe the apparatus by which they work.

This consists at the south end of a pair of plates, zinc and copper, forming a galvanic trough, placed under the keys; and at the north end of thirty steel magnets, about four inches long placed close behind the letters painted on the screen. The magnets move horizontally on axes, and are poised within a flat ring of copper wire, formed of the ends of the communicating wires. On their north ends they carry small square bits of black paper, which project in front of the screen, and serve, as opercula or covers to conceal the letters. When any wire is put in communication with the trough at the south end, the galvanic influence is instantly, transmitted to the north end; and in accordance with a welt known law discovered by Oersted, the magnet at the end of that wire instantly turns round to the right or left, bearing with it the operculum of black paper, and unveiling a letter. When the key, A, for instance, is pressed down with the finger at the south end, the wire attached to it is immediately put in communication with the trough; and at the same instant the letter A at the north end is unveiled, by the magnet turning to the right, and withdrawing the operculum. When the finger is re-moved from the key, it springs back to its place: the communication with the trough ceases; the magnet resumes its position, and the letter is again covered.

Thus by pressing down with the finger, in succession, the keys cor-responding to any word or name, we have the letters forming that word or name exhibited at the other end—the name Victoria, for instance, which was the maiden effort of the telegraph on Wednesday evening. In the same way, we may transmit a communication of any length, using an asterisk or cross, to mark the division of one word from another, and the comma, semicolon, or full point, to mark the breaks in a sentence, or its close. No proper experiment was made while we were present, to determine the time necessary for this species of communication; but we have reason to believe, that the letters might be exhibited almost as rapidly as a compositor could set them up in types. Even one-half or one-third of this speed, however, would answer perfectly well.

Galvanism, it is well known, requires a complete circuit for its operation. You must not only carry a wire to the place you mean to communicate with; but you must bring it back again to the trough. Aware , of this, our first impression was, that each letter and mark would require two wires, and the machine in these circumstances having sixty wires instead of thirty, its bulk and the complication of its parts would have been much increased. This difficulty has been obviated, however, by a simple and happy contrivance. Instead of the return wires extending from the magnet back to the keys, they are cut short at the distance of three inches from the magnet, and all join a transverse copper rod, from which a single wire passes back to the trough, and serves for the whole letters.

The telegraph, in this way, requires only thirty-one wires. We may also mention, that the communication between the keys and the trough is made by a long narrow basin, filled with mercury, into which the end of the wire is plunged when the key is pressed down with the finger. The telegraph, thus constructed, operates with ease and accuracy, as many gentlemen can witness. The term model, which we have employed, is in some respects a misnomer. It is the actual machine, with all its essential parts, and merely circumscribed as to length by the necessity of keeping it in a room of limited dimensions. While many are laying claim to the invention, to Mr. Alexander belongs the honour of first following out the principle into all its details, meeting every difficulty, completing a definite plan, and showing it in operation. About twenty gentlemen, including some of the most eminent men of science in Edin-burgh, have subscribed a memorial stating their high opinion of the merits of the invention, and expressing their readiness to act as a committee for conducting experiments upon a greater scale, in order fully to test its practicability. This ought to be a public concern. A machine which would repeat in Edinburgh words spoken in London, three or four minutes after they were uttered, and continue the communication for any length of time, by night or by day, and with the rapidity which has been described.--such a machine reveals a new power, whose stupendous effects upon society no effort of the most vigorous imagination can anticipate.
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