Fastened to the buntons at each side of each hoisting compartment are continuous strips of hard wood, from four to six inches square, reaching from the top of the shaft to its bottom. These are the “guides.” To each side of the carriage, which raises and lowers men and materials, is fastened an iron shoe, shaped like a small rectangular box without top or ends. This shoe fits loosely on to the guide, slides up and down it, and serves to keep the carriage steady while it is ascending or descending. This invention is due to John Curr of Sheffield, England, who introduced it as early as 1798. The ordinary carriage consists of a wooden platform with vertical posts at the middle of the sides united by a cross-beam at the top, and all solidly built and thoroughly braced. The posts are just inside of the guides when the carriage is in place, and are kept parallel to them by the shoes already mentioned. To the middle of the cross-beam is attached the end of a wire cable, from which the carriage is suspended, and by which it is raised and lowered. On the floor of the platform, which is planked over, a track is built uniform with the track at the foot and head of the shaft, and continuous with it when the carriage is at rest at either place. The mine car is pushed on to the platform of the carriage and fastened there by a device which clings to the axle or blocks the wheels. [Illustration: VERTICAL SECTION AT FOOT OF SHAFT, WITH ASCENDING CARRIAGE.] At the mouth of the shaft and projecting into it are the “wings,” “keeps,” or “cage rests,” which are pressed against the sides of the shaft by the ascending carriage, but spring back into place underneath it and support it while it is at rest. When the carriage is ready to descend the wings are withdrawn by hand levers. The safety carriage is now in general use in at least one hoisting compartment of every shaft. This carriage is built of wrought iron instead of wood; it has a bonnet or roof as a protection against objects falling down the shaft, and it has safety clutches or dogs to stop the carriage and hold it in place in case of accident by breaking ropes or machinery. Operators are required by the act of 1885 to provide safety carriages for the use of their employees, and also to keep movable gates or covers at the mouth of each shaft to prevent persons and materials from falling into the opening.