in the upward or downward mode it is of course understood that the bowl 14 can drop by its own gravity thus the purpose of bowl check and quick drop valve 28 is to in part relieve hydraulic pressure in conduit 27 during transporting operations of the tractor and scraper combination fluid is communicated from bowl cylinder jacks 16 back through the bowl check and quick drop valve 28 through a conduit 29 to a common return or common rail 30 and thence back to scraper control valve 26 for return to reservoir 22 by means of a conduit 31 similarly a conduit 32 communicates fluid selectively from scraper control valve 26 to an apron sequence valve 33 and in turn apron cylinder jack 18 for operation of apron 17 fluid is communicated from the apron cylinder jack 18 and apron sequence valve 33 by means of a conduit 34 interconnected with common rail conduit 30 a third main conduit 35 communicates with ejector cylinder jack 20 through a dump spool valve means such as dump spool valve arrangement 36 which would normally be positioned on the tractor 11 fluid is then communicated through a conduit 37 to valve means on the scraper for communicating to ejector cylinder 20 such valve means can be in the form of an unloading valve 38 which includes a valve spool 39 resiliently biased in.