ESSENTIAL MACHINES AND APPLIANCES 167 of guides that rigidly control the downward movement of the pattern away from its mould, or the upward lift of the box off its pattern. A little rapping Fig. 73.—Bottom Box rammed over Pattern, then tabled, turned over, and mould delivered E Fig. 74.—Top Box rammed over Pattern, embedded in Plaster of Paris, then turned over and delivered )E Fig. 75-—Mould Closed and Completed Figs. 73-75.—Cone Pulley moulded on a Darting & Sellers' Machine A, Pattern. B, Its mounting, c, Table of machine, D, Bottom box. E, Top box. is done, which does not sensibly enlarge the mould, like lateral hand rap- ping, but loosens the contact of the sand slightly. Either a hand mallet is used, striking blows on the table, or a pneumatic piston produces vibration.