1-158-619 - Oxford Science Archive/Heritage Images

Evangelista Torricelli, Italian physicist and mathematician, inventing the mercury barometer, 1643 (1873). Torricelli (1608-1647) demonstrated that liquid will rise in a tube unless the weight of the column of liquid is equal to the pressure of the air pressing on an equal section of the reservoir of liquid. The height of a column will depend on the density of the liquid used. Thus a column of water would be 9.75m (32 feet), while that of mercury which is approximately 13.5 times denser, would be .736m (29 ins). From The Atmosphere, by Camille Flammarion. (London 1873).