pressure measurement

Quicksilverbarometer

A quicksilverbarometer consists of a long glass tube that is closed on one end. The open end is being dipped into a bin containing quicksilver. A downward force is exerted onto the surface of the quicksilver caused by atmospheric pressure. The greater the pressure applied onto the surface of the quicksilver, the higher it rises within the tube.

The quicksilver barometer was invented by Evangelista Torricelli in the 17th centruy. He dicovered that the height of the quicksilver column in ther glass tube differs from day to day because there are fluctuations in the atmospheric pressure. 1 atm air pressure equals to 76 mm of quicksilver column.
Barometers can be used for weather forecast. High air pressure means nice weather, low air pressure hints to an upcoming storm.