1. IN A CONCENTRATING PLANT WHICH INCLUDES A LINE ADAPTED TO CARRY A STREAM OF MATERIAL AND A FIRST FIXED LAUNDER AT THE TERMINATION OF SAID LINE FOR RECEIVING THE STREAM OF MATERIAL THEREFROM, THE COMBINATION THEREWITH OF A SPLITTER FOR DIVIDING THE STREAM INTO TWO VARIABLE FRACTIONS, SAID SPLITTER COMPRISING A SECOND FIXED LAUNDER SPACED BENEATH SAID FIRST LAUNDER TO RECEIVE ONE FRACTION OF THE STREAM DIRECTLY THEREFROM, A THIRD FIXED LAUNDER OFFSET ENDWISE FROM SAID SECOND LAUNDER, A SWINGING LAUNDER SUPPORTED IN THE SPACE BETWEEN SAID FIRST AND SECOND LAUNDERS FOR CATCHING THE OTHER FRACTION OF THE STREAM BEFORE IT REACHES SAID SECOND LAUNDER AND HAVING AN OUTLET IN ITS END ABOVE SAID THIRD LAUNDER FOR DISCHARGING THE LATTER FRACTION THERETO, AND MEANS CONNECTED TO SAID SWINGING LAUNDER FOR ADJUSTING ITS POSITION TO VARY THE RELATIVE SIZE OF THE TWO FRACTIONS IN RESPONSE TO A CONTROL SIGNAL.