1911 Encyclopædia Britannica/Torricelli, Evangelista
The publication amongst Torricelli’s Opera geometrica (Florence, 1644) of a tract on the properties of the cycloid involved him in a controversy with G. P. de Roberval, who accused him of plagiarizing his earlier solution of the problem of its quadrature. There seems, however, no room for doubt that Torricelli’s was arrived at independently. The matter was still in debate when he was seized with pleurisy, and died at Florence on the 25th of October 1647. He was buried in San Lorenzo, and a commemorative statue of him erected at Faenza in 1864.
Among the new truths detected by him was the valuable mechanical principle that if any number of bodies be so connected that, by their motion, their centre of gravity can neither ascend nor descend, then those bodies are in equilibrium. He also discovered the remarkable fact that the parabolas described (in a vacuum) by indefinitely numerous projectiles discharged from the same point with equal velocities, but in all directions have a paraboloid of revolution for their envelope. His theorem that a fluid issues from a small orifice with the same velocity (friction and atmospheric resistance being neglected) which it would have acquired in falling through the depth from its surface is of fundamental importance in hydraulics. He greatly improved both the telescope and microscope. Several large object lenses, engraven with his name, are preserved at Florence. He used and developed B. Cavalieri’s method of indivisibles.
A selection from Torricelli’s manuscripts was published by Tommaso Bonaventura in 1715, with the title Lezioni accademiche (Florence). They include an address of acknowledgment on his admission to the Accademia della Crusca. His essay on the inundations of the Val di Chiana was printed in Raccolta d’autori che trattano del moto dell’acque, iv. 115 (Florence, 1768), and amongst Opusculi idraulici, iii. 347 (Bologna, 1822). For his life see Fabroni, Vitae Italorum, i. 345; Ghinassi, Lettere fin qui inedite di Evangelista Torricelli (Faenza, 1864); Tiraboschi, Storia della lett. it. viii. 302 (ed. 1824); Montucla, Hist. des math., vol. ii.; Marie, Hist. des sciences, iv. 133.