Experiments in telegraphy were carried out as far back as the year 1753, when it was proposed to transmit messages by representing the letters of the alphabet by combinations of sparks produced by a static machine; but these were of little practical value and nothing of any importance was accomplished until after the discovery of galvanic current. Many of these old experiments were very crude and appear somewhat ridiculous when compared with the methods of nowadays. The earliest proposal for an electric telegraph appeared in the _Scots’ Magazine_ for February, 1753, and shows several kinds of proposed telegraphs acting by the attractive power of electricity, conveyed by a series of parallel wires, one wire corresponding to each letter of the alphabet and supported by glass rods at every twenty yards. Words were to be spelled by the action of the electricity in attracting paper letters, or by striking bells corresponding to letters. The modern telegraph consists essentially of four things, namely: A battery which produces an electric current. A wire which conducts the electric current from one point to another. A transmitter for shutting the current off and on. An electro-magnetic receiving apparatus, which gives out in sounds, the signals made by the pulsations of the current from a distant point. The battery may be almost any form of battery. Gravity cells are preferred, however, for telegraph work. Heavy galvanized iron wire is usually employed as the "line." It is necessary to use non-conductors wherever the wire is fastened. Glass insulators placed on a wooden pin or bracket, which is fastened to the pole or building on which the wire is to be supported, are used for outside work. Inside of buildings, rubber tubes are used where the wires pass through walls, etc. The operation of a telegraph is not, as many people suppose, a complicated or difficult matter to understand, but is quite simple. The key is a contrivance for controlling the passage of the electric current in much the same manner as an ordinary switch. It consists of a steel lever, swung on trunnion-screws mounted in a frame, and provided with a rubber knob which the operator grasps lightly with the thumb and forefinger. On pressing the lever downward, a platinum point fastened on the under side of the lever is brought into contact with another point set into a rubber bushing in the base of the key, so that there is no electrical connection between the two points unless the key is pressed down or "closed," as it is often termed. The key is usually fastened to the operating bench by two rods called "legs." The lever is provided with screws which permit the stroke of the key to be very closely adjusted. [Illustration: Fig. 130.—A Typical Telegraph Key, showing the Various Parts.] The line wire and battery are connected to the key, so that no current can flow until the key is pressed and the contacts brought together.