In this jig, raw coal is conveyed to a wash box through sluices. Air pulsations are transmitted through valves to water in a compartment adjacent to the washing bed, causing the water in the wash box to rise. Pulsating water causes the incoming fuel to be loosely suspended in the water and permits heavier refuse to sink to the screen plate while suspended coal spills over into the second compartment. In the second 1930 compartment the process is repeated with the remaining refuse sinking to the screen and clean coal discharging to the dewatering screens.