The skip shown in the figure is suspended from a bent arm a attached to the wheel truck b, which is operated by an enclosed motor. The skip is slung on two wire ropes adapted to be wound on a double drum e by means of a second motor. Current is supplied to both motors through a live wire f and collector g. The skip is closed by bottom flaps h h, operated by a lever i, provided with a contact piece. The motors are switched in and out of action by portable switches, which enable the skips to be stopped and discharged at any desired point, and also to run at definite intervals.