A mechanical means for feeding coal into, and for burning coal in, a furnace. There are three basic types of stokers. Chain or traveling-grate stokers have a moving grate on which the coal burns; they carry the coal from a hopper into the furnace and move the ash out. Spreader stokers mechanically or pneumatically distribute the coal from a hopper at the furnace front wall and move it onto the grate which usually moves continuously to dispose of the ash after the coal is burned. Underfeed stokers are arranged to force fresh coal from the hopper to the bottom of the burning coal bed, usually by means of a screw conveyor. The ash is forced off the edges of the retort peripherally to the ashpit or is removed by hand.