Sailing Glossary - Term Cistern barometer

A mercury barometer in which the lower mercury surface is larger in area than the upper surface. The basic construction of a cistern barometer is as follows: A glass tube one meter in length, sealed at one end, is filled with mercury, and then inverted. The tube is mounted so that its mount penetrates the upper surface of a reservoir of mercury called the cistern of the barometer. See Fortin barometer, Kew barometer.