capable of assuming two positions when actuated by mechanical force. When this arm is horizontal and at right angles to the post it signifies "stop"; when it is nearly vertical it indicates "go on." As the arm cannot be seen at night, a lamp is provided on the post, and working with the arm is a frame containing coloured glasses, and termed "spectacles," which cause the lamp, to show a red light to indicate "stop," and a white or green light to indicate "safety," or "caution."
The signals are distinguished as "home signals," "distant signals," "starting signals," "advanced starting signals," and "disc signals." The home signal, as its name implies, is placed close to the point at which it is desired a train shall stop. The distant signal is placed at varying distances behind the home signal according to the gradient of the line and other circumstances, but on a straight and level railway it would be about 1,000 yards back, and its function is to repeat the action of the home signal, so that if the latter is at danger the driver has timely intimation of the fact, and can at once reduce the speed of his train so as to stop at the home signal. Distant signals are distinguished by a notch cut in the end of the arm. In working a Military railway it would be quite practicable to dispense with visible signals altogether and rely entirely upon the use of the telegraph; or, at all events, the two simple signals, the home and distant, as described, would probably suffice; but for the purposes of ordinary railways the introduction of the block telegraph system has necessitated the provision of starting and advanced starting signals. Starting signals are usually placed at the end of the platform at a station, and they indicate to the driver, by the lowering of the arm, when he may start his
