What is a Barometer?
A Barometer is a measuring instrument which measures air pressure. It indicates pressure trend such as Rising or Falling pressure. Generally a rising pressure indicates good sunny and dry conditions on the way, while a falling Pressure means stormy and wet conditions are approaching. An Italian scientist named Evangelista Torricelli built the first barometer in 1643.
The first barometers used a column of water in a tube 34 ft (10.4 m) long. This large tube was a bit inconvenient, and was soon replaced by Torricelli replaced with Mercury, which is denser than water and requires a tube about 3 ft (0.9 m) long. The mercurial barometer consists of a glass tube, sealed at one end and filled with pure mercury.