1. A MACHINE OF THE CLASS DESCRIBED COMPRISING AN OUTER CASING MEMBER HAVING AN UPPER GRAIN INLET FORMED AT THE TOP THEREOF AND A BOTTOM GRAIN OUTLET AND AIR DUCTS FORMED AT THE BOTTOM THEREOF, A CONICALLY SHAPED BARRIER ELEMENT HAVING A CYLINDRICAL SKIRT PORTION SUPPORTED IN SPACED RELATION TO THE INNER SIDE WALLS OF THE CASING TO DEFINE AN ANNULAR PASSAGEWAY FOR CONDUCTING GRAIN FROM THE GRAIN INLET DOWNWARDLY THROUGH THE CASING TOWARDS THE GRAIN OUTLET, A DEFLECTOR MEMBER AND A ROD ELEMENT ADJUSTABLY SUSPENDED FROM THE CONICALLY SHAPED BARRIER ELEMENT FOR SUPPORTING SAID DEFLECTOR IN SPACED RELATION TO INNER SIDEWALL PORTIONS OF THE CASING MEMBER TO PROVIDE A RESTRICTED AIR PASSAGEWAY THROUGH WHICH GRAIN FROM THE SAID ANNULAR PASSAGEWAY IS CAUSED TO PASS, SUCTION PIPE MEANS TRANSVERSELY LOCATED THROUGH THE SIDE OF THE CASING AND THE CYLINDRICAL SKIRT ELEMENT OF THE BARRIER PORTION AND VERTICALLY ADJUSTABLE ON SAID ROD ELEMENT FOR INDUCING A FLOW OF AIR FROM THE SAID AIR DUCTS UPWARDLY THROUGH THE RESTRICTED AIR PASSAGEWAY WHEREBY PARTICLES OF GRAIN AND GRAIN HULLS APPROACHING THE RESTRICTED PASSAGEWAY ARE TRAVELLED INWARDLY AND UPWARDLY INTO THE AREA ENCLOSED BY THE CONICAL BARRIER ELEMENT AND SAID SUCTION PIPE MEANS HAVING AN INNER EXTREMITY CURVED UPWARDLY TO PROVIDE AN ELBOW PORTION WHICH TERMINATES IN CLOSE PROXIMITY TO THE APEX OF THE CONICALLY SHAPED BARRIER ELEMENT AND WHICH FORMS AN ANNULAR ORIFICE THROUGH WHICH RELATIVELY LIGHT GRAIN HULLS MAY BE SELECTIVELY REMOVED WHILE RELATIVELY HEAVIER GRAIN PARTICLES ARE REJECTED.