84 THE ELECTRIC TELEGRAPH. 



attached to the axis of the pointer is arrested by coming 

 in contact with a depressed key, the currents which follow 

 are short-circuited. The hands of the indicators therefore 

 stand still upon the same place on the dials until the key is 

 raised and the short circuit removed. 



In the front of the indicator a contact lever is moved 

 between stops marked A and T. When the lever is placed on 

 A the arriving currents ring the alarm, the telegraph being 

 thrown out of circuit ; when it is placed on T, the alarm is 

 out of circuit and the indicator works. 



The working of this instrument, as well as the neatness 

 with which the whole is constructed, cannot be too highly 

 spoken of. The great advantage which it possesses over the 

 other step-by-step telegraphs, in which the coils or arma- 

 tures are stopped and started at every letter, is that its 

 currents are uniform, whereas in the other systems, at 

 starting and stopping, the operator cannot avoid moving 

 his handle slower than when driving it midway between 

 two letters, which very frequently gives rise to " skipping " 

 of the pointer. 



58. Simple Morse Circuit. In its simplest form the Morse 

 telegraph consists of a transmitting key and a recording 

 instrument, with intervening line wire, battery, and earth 

 connection. The purpose of the key is to close the circuit 

 of the battery conveniently for the formation of arbitrary 

 signals. The signals representing the letters, &c., consist 

 of combinations of two elementary marks, a dot and a dash. 

 The former is given by the momentary closing of the circuit, 

 and the latter by closing it for a longer time, by means of 

 the key. The signs are received at the distant station by 

 the corresponding attractions of the armature of an electro- 

 magnet, which marks them on a strip of paper in its vicinity. 

 The plan by which these arrangements are made at two 

 stations is represented in Fig. 44. At each of the stations, B 

 is a battery of voltaic pairs, connected between the point 1, 

 underneath the metallic lever K, and the earth. When the 

 lever K is not being manipulated, it is held by a spring upon 

 the metal point 2, between which and the earth are inserted 



