ELECTRIC TELEGRAPHS. 



405 



To send a current to another station, the handle (H) is moved to 

 one side, and the current sent will be positive or negative according to 

 the side to which the handle is moved. The handle turns the cylin- 

 drical arbor {a b), which is divided electrically into two parts by an 

 insulator in the middle of its length. Each of these parts has a pin 

 projecting from it, one pin being above, and the other below. These 

 are vertical when the handle is vertical, and are then doing no duty ; 

 but, when the handle is put to one side, the upper pin (which is at- 

 tached to b) makes contact with one of the tall springs (t t'), at the 

 same time pushing it away from the metallic rest (k), and thus putting 

 it out of connection with the other tall spring ; while the lower pin 

 (which is attached to a) makes contact with one of two short springs 

 (T T), only one of which is shown in the figure. There is permanent 

 connection between a and the negative pole of the battery through 

 the spring s, and between b and the positive pole through the spring s'. 

 In the position represented in the figure, a serves to connect the nega- 

 tive pole of the battery with the earth, and b serves to connect the 

 positive pole with the spring t', down which the current passes from 

 the point of contact of the pin, and then through the coil to the line- 

 wire at L. The needle of the sending station is thus deflected to the 

 same side as that of the receiving station. 



Fig. 4. 



Breguet's Indicator. 



If the handle were moved to the other side, b would serve to con- 

 nect the positive pole with the earth, and a would establish connection 

 between the negative pole and the coil, which is itself connected with 

 the line-wire. 



Since the English telegraphs came into the hands of the post-office, 

 the alphabet devised by Wheatstone and Cooke has been given up, and 

 the Morse alphabet, which we give in a later section, adopted in its 



