but when the delivery is under pressure from nozzles 16 essentially parallel with the uppermost end of the screening surface effective dewatering without substantial removal of solids will occur even though the slots 25 are widest in this area then as the thickening slurry continues down the screening surface it will approach the area of minimum radius curvature and minimum slot width which will tend to introduce a retarding action on the flow of the slurry for effective dewatering through the narrow slots without substantial loss of solids screen assembly 11 may be mounted for operation in any conventional screening apparatus but it is desirable to provide for adjustment of the relation of its screening surface to the vertical as shown in fig1 screen assembly 11 is mounted in housing 20 by supporting it on the partition 30 between discharge means 12 and 13 and at the top 31 of housing 20 in this way a screen assembly 11 can be readily replaced when it is worn and screen assemblies of different characteristics can be interchanged as desired housing 20 is supported for rotational movement by a hinge pin or rod 33 which passes through the side walls 34 of housing 20 and is attached thereto by welding or the like and through holes in frame 35 by mounting housing 20 for rotation about the axis of rod 33 the angularity of the surface of screen assembly 11 seated in housing 20 can be adjusted as desired in accordance with input slurry conditions and the desired screening results or effects in order to hold housing 20 in the selected angular positions a hole.