410 



THE POPULAR SCIENCE MONTHLY. 



ployed are of two lengths, one being made as short as possible (-), 

 and called a dot, and the other being about three times as long ( ), 

 and called a dash. The opposing spring (D) restores the armature to 

 its original position the moment the current ceases. 



Fig. 10. 



Morse's Telegraph Modified Form. 



Morse's key (Fig. 11) is simply a brass lever, mounted on a hinge 

 at A, and pressed up by the spring f. When the operator puts down 

 the key, by pressing on the button (K) with his finger, the projections 



Fig. 11. 



Morse's Key. 



(c d) are brought into contact, and a current passes from the battery- 

 wire (P) to the line-wire (L). When the key is up, the projections (a b) 

 are in contact, and currents arriving by the line-wire pass by the wire 

 R to the indicator or the relay. By keeping the key down for a longer 



