Consists of a ‘J’ tube mounted on a wooden stand approx. 840mm high. The closed limb of the ‘J’ tube is approx. 400mm long with 1mm bore & the open limb is approx. 780mm long with 8mm bore. A scale is fitted to the stand graduated from 0 at the lower end to 80cm at the top. A loose fitting plunger is pushed into the open limb of the ‘J’ tube by displacement; the height of the mercury can be adjusted from about -50mm to +450mm relative to the closed end.