Evangelista
Torricelli

Torricelli
detail of a portrait by an unknown artist 

(b. Oct. 15, 1608, Faenza, Romagnad. Oct. 25, 1647, Florence),
Italian physicist and mathematician who invented the barometer
and whose work in geometry aided in the eventual development of integral
calculus. Inspired by Galileo's
writings, he wrote a treatise on mechanics, De Motu ("Concerning
Movement"), which impressed Galileo. In 1641 Torricelli was invited
to Florence, where he served the elderly astronomer as secretary and assistant
during the last three months of Galileo's life. Torricelli was then
appointed to succeed him as professor of mathematics at the Florentine
Academy. 
Two years later, pursuing a suggestion by Galileo, he filled
a glass tube 4 feet (1.2 m) long with mercury and inverted the tube into
a dish. He observed that some of the mercury did not flow out and that
the space above the mercury in the tube was a vacuum. Torricelli became
the first man to create a sustained vacuum. After much observation, he
concluded that the variation of the height of the mercury from day to day
was caused by changes in atmospheric pressure. He never published his findings,
however, because he was too deeply involved in the study of pure mathematicsincluding
calculations of the cycloid, a geometric curve described by a point on
the rim of a turning wheel. In his Opera Geometrica
(1644; "Geometric Works"), Torricelli included his findings on fluid
motion and projectile motion.
Copyright 19941998 Encyclopaedia Britannica 
