Abstract: Charge images on a moving substrate such as a photoconductive belt surface are developed by being passed over two magnetic developing rollers in succession, which include nonmagnetizable cylinders rotatable in opposite directions about stationary magnet systems and are spaced apart outside each other's zone of influence in the upper region of a trough-shaped reservoir. The reservoir has oppositely sloped side walls converging to a bottom for holding a supply of developing powder, from which powder is supplied into a zone between the developing rollers for attraction to their surfaces by at least one magnetic transfer roller located between them and the bottom.