An engraving depicting a hydraulic press. Material to be compressed is placed on a plate which is raised and lowered by a piston, P which descends into the tank of water, B. B is connected to a force pump (right) using a leaden tube, K. When the pump handle, M, is operated and water is taken up from the reservoir, A, the pressure in B rises, lifting the piston, P, and compressing blades. Dated 19th century.