From Mary Bellis,
Your Guide to Inventors.
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Barometer - Pronunciation: [b u rom´ u t u r] - a barometer is an instrument for measuring atmospheric pressure. Evangelista Torricelli invented the barometer, also known as the "Torricelli's tube".

Biography - Evangelista Torricelli

Evangelista Torricelli was born October 15, 1608, in Faenza, Italy and died October 22, 1647 in Florence, Italy. He was a physicist and mathematician. In 1641, Evangelista Torricelli moved to Florence to assist the astronomer Galileo.

The Barometer

It was Galileo that suggested Evangelista Torricelli use mercury in his vacuum experiments. Torricelli filled a four-foot long glass tube with mercury and inverted the tube into a dish. Some of the mercury did not escape from the tube and Torricelli observed the vacuum that was created.

Evangelista Torricelli became the first scientist to create a sustained vacuum and to discover the principle of a barometer. Torricelli realized that the variation of the height of the mercury from day to day was caused by changes in the atmospheric pressure. Torricelli built the first mercury barometer around 1644.

Evangelista Torricelli - Other Research

Evangelista Torricelli also wrote on the quadrature of the cycloid and conics, the rectifications of the logarithmic spiral, the theory of the barometer, the value of gravity found by observing the motion of two weights connected by a string passing over a fixed pulley, the theory of projectiles and the motion of fluids.