234 
THE TELEGRAPH. 
The contacts are made by a piece oscillating between two 
stops A, b, fig. 167, placed very close together, and one of these 
closes the circuit of the local battery. The armature is always 
free to move, even when the contact-piece touches the stop, or 
in other words the resting position is very near the contact 
position. 
This apparatus is very quick, and is daily used at Marseilles 
for communicating with London, with only one transference at 
Paris. This speed is certainly the highest that can be attained 
on a telegraphic line of such length. It is never less than 
thirty words per minute, and it has often reached forty. The 
relay requires no adjustment, and the less it is meddled with 
the better it works. A modification of this relay, devised by 
M. Theiler, also gives excellent results, both with sub-marine 
and overhead lines. 
The manipulator or key used in the Morse apparatus is of a 
very simple construction, when, as with overhead lines, only 
one current goes to the formation of a signal. It is represented 
in fig. 168. A lever b, turning on l, is kept in normal position 
by the spring n. The line is connected at L, and a current 
arriving through it passes through A to the receiving apparatus. 
When the knob c is pressed, the communication is interrupted 
at A, and the receiving apparatus is put out of circuit ; at the 
