242 
THE TELEGRAPH 
position until it is reversed by the thrusts of k and r'. Thus 
the lever r causes the rods s and M to regularly move up and 
down, by making the arms A and b oscillate ; so, while these 
rods continue in action, the disc n vibrates backwards and 
forwards, carrying with it the levers c and z. 
The stud 1 of the lever n is in communication with the 
earth, and 2 with one of the halves of the disc n, the other 
half of which communicates with the line. When the strip of 
paper is not in its place, these studs are in constant and un¬ 
interrupted contact with the arms of the lever a and b, which 
are plated with platinum and metallically connected with the 
frame of the apparatus s and s', and thus the circuit is com¬ 
pleted, and transmits a series of reversed currents that produce 
dots at the receiving end of the line. 
At the places where the strip is not perforated, it limits the 
play of the rods, and the elbow levers A and b no longer follow 
the studs to the extent of their motion : the disc d ceases to 
move ; and the communication being thus interrupted, no 
