The Italian mathematician and physicist Evangelista Torricelli (1608-1647) invented the mercury barometer and made important contributions to calculus and the theories of hydraulics and dynamics.

Evangelista Torricelli was born in Faenza on Oct. 15, 1608. Left fatherless early in life, he was educated by his uncle, who was in monastic orders. In 1627 his uncle sent him to Rome to study mathematics and natural philosophy under Benedetto Castelli, professor of mathematics at the Collegio di Sapienza, who had been one of Galileo's pupils.

Torricelli spent the next 10 years in study. He corresponded with Galileo and studied his writings. He was especially impressed by the Dialogues concerning Two New Sciences (1638) and at once generalized Galileo's analysis of projectile motion. His conclusions on this and other subjects were set down in his book De motu gravium (1640; published 1644). Galileo invited Torricelli to Florence in 1641, and he became the amanuensis and companion of the great...