 The ladder carries a circular tumbler at its lower end and a series of rollers on its upper side to support the loaded buckets.The top, or driving, tumbler is normally hexagonal in shape and is driven by electric motors mounted on either side of the ladder.The size of a dredge is designated by the capacity of its individual bucket which can be up to 20 cubic feet but, in the case of the Nettle Creek dredge is 12 cubic feet.