Note 4 — NOTES.1

Torricelli was a physicist and mathematician who lived from 1608 to 1647. He was a disciple of Galileo, and acted as his amanuensis for three months before Galileo’s death. He was then nominated as grand-ducal mathematician and professor of mathematics in the Florentine Academy. In 1643, he made his most famous discovery. He found that the height to which a liquid will rise in a closed tube, depends on the specific gravity of the liquid, and concludes from this that the column of liquid is sustained by atmospheric pressure. This discovery did away with the obscure idea of a fuga vacui, and laid bare the principle on which mercurial barometers are constructed. For a long time the mercurial thermometer was called the “Torricellian tube,” and the vacuum which the barometer includes is still known as a “Torricellian vacuum.”8