approaching locomotive knows that the block he is about to enter is clear and also that the rails of the section before that is clear as well. The lower arm, or "semaphore," stands for the second block, and if it is horizontal the engineer knows that he must proceed cautiously because the second section already has a train in it; if the upper arm is straight the "runner" knows that a train or obstruction of some sort makes it unsafe to enter the first block, and if he obeys the strict rules he must stay where he is until the arm is lowered At night, red, white, and green lights serve instead of the arms: white, safety; green, caution; and red, danger. Accidents have sometimes occurred because the engineers were colour-blind and red and green looked alike to them. Most roads nowadays test all their engineers for this defect in vision. In spite of all precautions, it sometimes happens that the block-signals are not set properly, and to avoid danger of rear-end collisions, conductors and brakemen are instructed (when, for any reason, their train stops where it is not so scheduled) to go back with lanterns at night, or flags by day, and be ready to warn any following train. If for any reason a train is delayed and has to move ahead slowly, torpedoes are placed on the track which are exploded by the engine that comes after and warn its engineer to proceed cautiously. All these things the engineer must bear in mind, and beside his jockey-like handling of his iron horse, he must watch for signals that flash by in an instant when he is going at full speed, and at the same time keep a sharp lookout ahead for obstructions on the track and for damaged roadbed. The conductor has nothing to do with the mechanical running of the train, though he receives the orders and is, in a general way, responsible. The passengers are his special care, and it is his business to see that their getting on and off is in accordance with their tickets. He is responsible for their comfort also, and must be an animated information bureau, loaded with facts about every conceivable thing connected with travel. The brakemen are his assistants, and stay with him to the end of the division; the engineer and fireman, with their engine, are cut off at the end of their division also.