For the past forty or fifty years movable ladders have been used in many mines both in Europe and America, though less extensively in this country than in the former. In England they are called “man-engines,” and are constructed on a principle of reciprocal motion of two parallel rods. The rods are placed about fifteen inches apart, and steps and handles are so arranged as to be at about the ordinary height of a man. By the action of the steam engine one of the rods is raised to a certain height, while the other is lowered for the same distance. During the movement of the crank over its turning point, the miner goes from the step on which he stands to the opposite step. Another stroke of the engine is made, and the rod moves in the opposite direction, and is followed by a fresh movement of the miner. Whether he goes up or down, the man rises or descends without any fatigue, and the journey is made in a very short time. Many of these engines have been abandoned for the safety cage. The rate at which the men were lifted by them was seventy-two feet a minute, or a little less time than would be required for ascending by the rope. Another machine in use in Belgium and France is a single rod, and in place of the steps there are fixed platforms holding two men each. The length of stroke of the machine is about nine feet, and it will make twelve or fifteen strokes a minute. [Sidenote: MOVABLE LADDER.] The man travelling by it must be very watchful. He must pass from the movable ladder to the landing stage or platform, and watch for a new stroke or step upon the ladder. To avoid accidents he must use great caution, and no hesitation. The slightest embarrassment may cause a very serious accident, and the sudden return motion may kill the traveller on the spot. From the bottom of the shaft of a mine the men scatter in various directions to their work, or are distributed among the different levels. A shaft is perpendicular, while the level is horizontal. The dangers in the shaft have already been described. Strictly speaking, no dangers of the same sort are liable to occur in the levels. True, there may be falls of rock or coal, or whatever other substance forms the roof of the mine; but they generally occur in consequence of the carelessness of some person on the same level, and not above or below.