592 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



time, and this speed is regulated by the rapidity with which currents 

 can be transmitted through the wire without coalescing or interfering 

 with each other. Wheatstone's automatic telegraph consist^ of three 

 parts, one for the preparation of the perforated paper ribbon, by which 

 the succession and sequence of the currents representing the message 

 are regulated ; another, the "transmitter," for passing the currents so 

 grouped together into the line wire, and the third, the " receiver/' the 

 apparatus for recording and transforming the currents so passed into 

 the line into symbols representing letters, words, and sentences. The 

 message to be sent is first punched out in holes representing the "dot " 

 arid "dash " of the Morse alphabet, on a continuous paper ribbon by 



FIG. 384. The " Perforator," for cutting out the message on the paper ribbon 



means of an instrument called the " perforator," Fig. 384. Each of the 

 three finger-keys on depression perforates certain small round holes in the 

 paper ribbon, the right hand key. two large holes opposite each other 

 with a small hole in the middle, being representative of the " dot, 5 ' 

 the left hand key two large holes alternate over two small centre 

 holes, being representative of the " dash ;" the centre key perforates 

 a single centre small hole, this centre hole being for the mechanical 

 spacing of the holes and groups of symbols ; it is also necessary for 

 ensuring the regular motion of the paper ribbon through the 

 " transmitter." 



