(under subclass 422) Apparatus including movable permeable or perforated supports for material, other than rotating endless belts, and means for sending pulsating or interrupted gaseous currents through the support and the material, so that the heaviest constituents of the material may settle as a stratum, while the lighter constituents may either form relatively displaced strata or be removed by the gaseous currents, there being no substantial movement of the heaviest constituents along the support or the heaviest and the lighter constituents both moving in the same direction toward discharge.
