SCIENCE IN THE INDUSTRIAL WORLD 



upon the iron core or magnet corresponding precisely 

 with the pressing and raising of the key-button, since 

 the passage of current is practically instantaneous. If 

 this button arrangement, which is called a "trans- 

 mitter," is placed at some distance from the magnet and 

 hammer, it is obvious that a person working the button 

 of the transmitter can make certain signals to persons 

 within hearing of the hammer strokes upon the magnet. 

 If certain signals were mutually agreed upon, one tap 

 of the hammer indicating the letter A, two taps the letter 

 B, etc., messages could be sent and received with ab- 

 solute accuracy. 



Such an arrangement is the underlying principle of 

 the Morse telegraph, although when worked out in 

 practical detail and perfected, as was done by Morse, 

 the apparatus is much more complicated. Morse found, 

 for example, that after a certain length of wire had been 

 used the receiving instrument no longer responded to 

 the making and breaking of the current. To overcome 

 this he found it necessary to strengthen and increase 

 the current at certain intervals with "relays," which 

 were referred to a moment ago. This was one of the 

 novel and important factors of his discovery. 



Another important feature was a method of recording 

 the messages received other than by sight or hearing. 

 Morse perfected such a recorder, by which the tappings 

 of the receiving hammer were impressed upon a strip of 

 paper so that an operator might interpret the message 

 from the strokes and intervals of the receiver, or might 

 have it as a written impression in dots and dashes on a 

 strip of paper. 



