VOLTAIC ELECTRICITY. 



249 



395. The Electric Telegraph. The electric tele- 

 graph consists essentially of an electro-magnet and a " key " 

 placed in the circuit of a battery. The key is an instru- 

 ment by which the circuit may be easily broken or closed 

 at will. The armature of the magnet is supported by a 

 spring, which lifts it when the circuit is broken. When 

 the circuit is closed, the armature is drawn down. Thus 

 the armature may be made to vibrate up and down at the 

 will of the person at the key. The armature may act upon 

 one arm of a lever, the other end of which, being provided 

 with a style or pencil, may be pressed a.gainst a strip ot 

 paper drawn along by clock-work. Thus the pencil may 

 be made to record, upon the moving paper, a series of dots 

 and lines at the pleasure of the operator at the key perhaps 

 hundreds of miles away. When the two stations are 

 several miles apart, one of the wires is dispensed with, the 

 circuit being completed by the earth. 



396. Morse's Alphabet. The inventor of the 

 electric telegraph was an American, S. F. B. Morse. The 

 system of signals devised by him is given below : 



LETTERS. 



FIGURES. 



1 ---- 



2 ----- 



3 ----- 



4 ----- 



5 --- 

 C ...... 



7 ---- 



8 ----- 



9 ---- 

 _ 



To prevent confusion, a small space is left between successive 

 letters, a longer one between words, and a still longer one between 

 sentences. Telegraph operators soon become so familiar with this 



