railway signals. 
2?3 
or other points where the trains must stop, so that the engine- 
drivers may be able to stop the train if required, by slackening 
speed as they pass the signal. This distance varies from 500 
to 800 yards, and the signal is worked at this distance by 
means of a wire passing over pulleys. 
The signals are not always visible at the place from which 
they are worked ; it was formerly usual to place near the lever 
a small duplicate signal put in motion by the disc itself, so 
that the signalman might be certain that the latter was at the 
proper position. 
This duplicate signal has long been advantageously super¬ 
seded by an electric bell. The disc is fitted with a horizontal 
lever which it carries round as it turns. When the line is 
blocked, this lever is in contact with a piece of metal by which 
the circuit of a galvanic bat tery is closed, and a current causes 
a bell to ring continuously, either near the working lever or at 
the station. As the circuit is closed only at the time when the 
disc is perpendicular to the rails, the sound of the bell will 
indicate with certainty when the signal is against the approach 
of a train. If, on the other hand, the electric bell does not act 
when the lever is in the proper position, this will be an indica¬ 
tion that the apparatus has in some way become deranged, 
and an employe will be sent to put it right. 
At night also the tinkling of the electric bell will show 
plainly when the line is blocked by the signal, and it has been 
proposed to so arrange the electric circuit that it should be 
broken in the event of the lamp attached to the signal going 
out—an accident which, however, rarely happens. 
These stopping signals are quite sufficient on railways with 
double lines, and they are independent of the telegraph, which 
plays quite another part. 
On railways with only one line, the German system of 
electric-bell signals was several years ago adopted in France. 
These bells serve to indicate to the railway staff, both at the 
station and along the line between the stations :■—First, the 
departure of each train ; second, when help is required ; third, 
the necessity of immediately stopping all the trains ; fourth, 
runaway waggons on the line. 
On some lines each station is provided with two bell 
apparatus—one at each end of the station ; and an electric 
