Abstract: A feeder comprising in combination a vessel (10) of substantially circular cross section that contains an en-masse conveyor (11) that is constrained to pass through a trough (16.sub.1, 16.sub.2) spaced from the internal wall of said vessel so that material being conveyed from an inlet (10.sub.1) in said vessel (10) to an outlet (14.sub.2) in said vessel (10) by said conveyor does not come into rubbing contact with said wall.