Torricelli Barometer: Column of mercury in bell jar.

Torricelli Barometer: Column of mercury in bell jar. A long glass tube, sealed at one end, is filled with mercury. The open end sits in a dish of mercury. The mercury drops until the pressure due to its own weight inside the tube (at height h) is equal to the atmospheric pressure outside. The height h measures directly the atmospheric pressure. If a vacuum pump is used, the mercury column drops until the level of the mercury inside the tube is the same as the level of the mercury in the dish. Note: let the air back into the vacuum plate slowly. FLUID STATICS.