born Oct. 15, 1608, Faenza, Romagna
died Oct. 25, 1647, Florence
Italian physicist and mathematician, inventor of the barometer .
He served as secretary to Galileo during the last three months of the latter's life and was appointed to succeed him at the Florentine Academy. Two years later, pursuing a suggestion by Galileo, he filled a glass tube 4 ft (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. 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. His work in geometry aided in the eventual development of integral calculus.