62 THE ELECTRIC TELEGRAPH. 



teeth of the ratchet-wheel G 5 * If, on the contrary, the cam 

 has to retard the motion, the click pulls the ratchet-wheel 

 backwards, for which purpose the latter is not made rigid on 

 the axis, but is formed of a disc held between leather washers 

 supported by two plates of metal, fixed on the hollow shaft G-. 



The electric circuits of the apparatus are very simple. The 

 bottom of the vertical shaft Q is connected to earth, and the 

 upper part to one end of the coils of the electro-magnet, the 

 other end being to line. One pole of a battery is connected 

 to the levers k of the contact pins, the other pole to earth. 

 At two corresponding stations the plates of the batteries 

 must always be looking the same way, because the home 

 apparatus is intended always to work as well as that of the 

 distant stations, and the armature of its magnet is only 

 liberated by currents in one direction. 



When a current arrives, therefore, from the line, it passes 

 first through the coils B of the magnet, then through the 

 vertical shaft Q, which it descends, and goes over from the 

 screw in the jointed arm v to the resting piece r y and from 

 this to earth. When a current is to be transmitted, the 

 operation consists principally in interrupting the earth 

 circuit, and in inserting the battery into the break. This is 

 done by the contact pins and jointed arm of r. A key being 

 depressed, the arm r in its journey rides over the pin, and its 

 screw is lifted up from contact with r, which breaks the 

 direct earth circuit. At the same time the contact of r with 

 the pin k, which is in communication with a pole of the 

 battery through the lever K, sends a current from the battery 

 (K k, r Q), through the coils of the magnet into the line, &c. 



Suppose two such apparatus, properly adjusted, at the 

 extremities of a line of telegraph, the clockwork wound up, 

 the electrical connections properly established, and the type- 

 wheels locked. The employe who desires to transmit presses 

 down the blank key of his instrument ; this pushes up the 

 corresponding contact-peg in the circle K, and when the 

 chariot arrives over the pin, the extremity of the piece r 

 rides over it, separating the earth contact and introducing 

 the battery into the line circuit. The current passes through 



