82 THE ELECTRIC TELEGRAPH. 



57. Wlieatstone* s Universal Telegraph. This is another 

 form of step-by-step telegraph, the invention of Professor 

 Wheatstone. During the last few years it has obtained con- 

 siderable employment on private lines, being found at nearly 

 all the ends of the network which Professor "Wheatstone has 

 helped to spin over the metropolis. 



It consists of two parts the " communicator " and the 

 " indicator." 



The communicator is contained in a small square box, on 

 the upper surface of which is a raised dial-plate, surrounded 

 by thirty equidistant keys radiating from the same centre. 

 Upon the dial-plate are marked the twenty-six letters of 

 the alphabet, three points of punctuation, and an asterisk ; 

 in an inner circle are the nine numerals and a cross on each 

 side. A hand or pointer, turning on an axis in the centre 

 of the dial, rotates in connection with the handle in the 

 front, and may be arrested at any letter while the handle is 

 being turned, by depressing one of the keys or buttons. 



Inside the box is a fixed permanent horse-shoe magnet, 

 placed horizontally, carrying, on its poles, four soft iron 

 cylindrical cores with their coils of wire, arranged at equal 

 distances from each other in the circumference of a circle. 

 On an axis passing through the centre of this circle, in 

 connection with the handle, revolves a soft iron armature 

 whose breadth is a little greater than the distance between 

 two adjacent cores. When the armature revolves, therefore, 

 it approaches one pole as it recedes from the one diagonally 

 opposite, and thus induces simultaneously in the two coils 

 currents in the same direction. 



A small circular chain is placed horizontally underneath 

 the keys, and becomes slightly bulged to the extent of its 

 slack when a key is pressed down. As soon as another 

 key, however, is pressed down, the chain straightens itself 

 underneath the first key and lifts it up. The purpose of 

 the keys is to arrest at pleasure the march of the pointer 

 round the dial, and to short-circuit the currents at any 

 letter. This is done by an arm, attached to the axis which 

 carries the pointer on the dial, coming in contact with the 



