The apparatus consists of a standard brass permeability cell, inner diameter 12.7 mm, with a perforated metal disc and a piston, a U-tube glass manometer with rubber coupling for the permeability cell, mounted on a wooden stand, a latex rubber tube, 30 cm long, 100 ml of dibutyl phthalate liquid, a suction ball. Additional instruments for the whole experiment, namely. Philtre paper discs, electronic precision balance (1 mg), standard cement, stopwatch, etc. are available at extra cost.