MORSE'S TELEGRAPH. 723 



That part of a Morse's telegraph which has just been 

 described is usually called the 4 indicator.' For closing 

 and breaking the circuit, the ' communicator,' or ' key,' 

 shown in fig. 364, is used. It consists of a small wooden 



Fm. 364 (i real size). 



base, which acts as support for a metallic lever, mova- 

 ble on the axis a. The end b of the lever is ordinarily 

 drawn downwards by the spring f, but by pressing 

 the handle &, the other arm of the lever is lowered and 

 b is raised. At c and b there are small studs of 

 steel or platinum, attached to the lever, which may be 

 made to strike upon similar studs e and d, and thus 

 to produce ' contact/ either between c and e when the 

 key is pressed clown, or between b and d when the key 

 is at rest. The metal pieces d and 0, as well as the 

 piece ^, which supports the axis of the lever, are pro- 

 vided with binding screws for attaching the conducting 

 wires; these are usually simple screws with broad flat 

 heads, which clamp the wires placed beneath them. 



For the telegraphic connection of two stations, I. 

 and II. in fig. 365, there are required two batteries, 

 two indicators, two communicators or keys, and a 

 complete circuit formed by two conductors. One 

 of these is formed by the ' line wire,' usually of iron, 

 while the earth itself is used as the second conductor. 

 For this purpose two large plates of copper, e l and e. 2 



3 A 2 



