CHAPTER VII. 



Signals Interlocking Block Telegraph and Electric Train Staff Instruments. 



Signals. Railway tradition alleges that on one of the early lines 

 opened for passenger traffic, the precautions for public safety 

 were considered to have been fulfilled by providing a man on 

 horseback to ride along the track between the rails in the front 

 of the locomotive engine, to give warning to persons strolling on 

 the line, and to check the advance of the train when necessary. 

 A very short experience of this method of working proved that 

 the full capabilities of the locomotive could not be obtained from 

 a restricted speed of seven or eight miles an hour, and a more 

 comprehensive system of signalling had to be devised. By fencing 

 in on both sides of the line, the public were prevented from making 

 a general highway or promenade along the railway, and the 

 problem was reduced therefore to the signalling for the trains 

 alone. 



Flags of different colours, held by flagmen stationed at suit- 

 able places, answered the purpose for a while, or so long as the 

 authorized running speed did not prevent the train being brought 

 to a stand after sighting a flag warning the engine-driver to stop. 

 As speeds were increased, a longer or more distant view of signals 

 became imperative, and tall posts, or semaphore signals, were 

 introduced. Well-defined blades or discs placed on high posts 

 were easily worked from the ground-level, and could be seen for 

 long distances, thus enabling the trains to be controlled or brought 

 to a stand before reaching the signal. The efficiency of the 

 principle once recognized, improvements and additions were 

 made from time to time, until we have the simple acting tall 

 semaphore signal so universally in use at the present time. The 

 position of the signal arms or blades in the daylight, and the 

 colours shown by the lamps at night, form the code of signals for 

 the proper working of the train service ; and as the signal arms 

 and lamps are both worked simultaneously by the same gearing, it 



