The great simplicity of this American telegraph is the use of the ground as the return conductor: thus rendering only one wire needful. It also proves a better conductor than wire, the current seeming to prefer it. Communication is easily established with it: in cities a gas pipe answers ; any where a metal plate, buried in the ground, or immersed in a river, effects the object. A hair wire suspend ed from the travelling wire and dipping in a river is sufficient to break the circuit as effectually as if the wires were cut. No matter how many stations intervene between the termini, there is no altera tion produced on the current when the wires are well insulated. On one of the lines there are 16 stations, each of which unite with each, or all the others, each receiver preserving a closed circuit, while the transmitting operator manipulates with his key. The average price of trans mission is 25 cents for ten words 100 miles ; this is much below the Prussian tariff. In England the charge is so high as to leave its benefit only in the hands of a few, A skilful operator knows by the sound of the cull in his office where the intelli gence comes from, and the abbreviations are so numerous that a ready penman cannot keep up with the delivery of a message : as many as 25,000 letters have been transmitted in an hour and a half by two instruments and wire. Changes of weather in the earth's surface, and gene ral disturbance of atmospheric electrical equilibrium renders the insulation imper.
feet and transmission of messages are put a stop to.
The country between Mobile and New Orleans is an instance of the difficulty of writing through a damp atmosphere, for although it is only 190 miles by telegraph line, yet it is with difficulty they can write that distance, and it requires the most strict attention to the line to keep it in working order, while on the same line they work in many places over 400 miles. House's Telegraph machinery is much more complex than Morse's, and costs in construction ten times as much. Its object is to make at one end of a wire the revolution of a disc, upon whose edge the Roman letters are raised synchronous with the operations of a lettered finger board at the other end of the wire. So that at the touching of A on the finger board, the wheel presents and impresses A on a slip of paper. The paper is moved, so that the letters succeed each other, as in ordinary printing, and a visi ble impression is made by the arrange ment similar to the manifold writer. The operator at New-York plays upon his ma chine, like a lady at her piano, and at Bos ton a little arm is seen revolving round and round, clicking and printing, in black letters, R, 0, Y, A, L. E, H, 0, U, S, E, on a strip of paper. On Morse's telegraph the messages have to be re-written by a penman into plain English.
Bain's telegraph.—Bain, in 1843, took out the patent for his copying telegraph.
The machine consists of a drum, on which is rolled a card, which, with a weight attached, moves a train of wheels. In connection with the drum, by pinion and axle and bent wheel, hangs a rod, on which is placed a revolving pendulum supported by a flexible cord with a screw attached, which can raise or lower the pendulum ; to another wheel, the axle of which is carried through the print plate of the instrument two lesser wheels are attached, upon which there are metal cy linders movable by a pulley and axle, which winds a silk cord fastened to a steel rod to the extremity of which is a binding screw to hold a fine wire or needle. This latter can be brought into contact with the cylinders, any non-con ducting substance interposed between the cylinders and the needle interrupts the current, and the apparatus thus be comes available for copying work. The motion given to the wheelwork by the weight is rendered uniform by the revolv ing pendulum. A peculiarity in the form of the escapement gives it an isochron ous motion by means of a vertical pen dulum, the length of which is regulated by screws, so as to check any deviation in rate of motion of the revolving pendulum. Electromagnets are thus dispensed with. This apparatus is used for transmitting and receiving ; for transmission, the Message may be written on tinfoil or paper, coated with Dutch metal, varnish, or any non-conductor, or by moistening the has of the paper and then writing on the metal surface with a blunt style. This communication is then laid on one of the cylinders, and a cylinder of the ponding instrument at the receiving sta tion is covered with chemically prepared paper. A current of electricity being generated by a battery at the transmitting station, is passed through the instrument there and conveyed by a single wire to the corresponding instruments at the re ceiving station, whence it returns back through the earth to the battery. As the cylinders rotate, the arm descending with the needle traces a continuous spiral line from the top to the bottom of the cylin der which becomes a permanent mark on the chemically prepared paper, broken at intervals, corresponding to the marks made with the non-conducting material on the metallized paper.
The writing may be made with a con ducting material on a non-conducting surface, when the marks composing the received communication will be repre sented by dots and lines upon a plain ground.
The chemical paper consists of fine thin paper soaked with a solution of yellow prussiate of potash, and afterwards dip ped in weak nitric acid. This tends to facilitate the decomposition of the prus siate, the acid being a good conductor; blue mark is left where the needle touches.