TORRICELLI (EVANGELISTS,) in bio graphy, an illustrious mathematician and philosopher of Italy, was born in 1608, and trained up in the knowledge of clas sical literature. The bent of his mind, however, led him to the pursuits of natu ral philosophy, which he studied under father Benedict Castelli, who had been the scholar of the great Galileo, and was professor of mathematics at Rome. Tor ricelli made such progress under this master, that having read Galileo's "Dia logues," he composed a "Treatise con cerning Motion" upon his principles. Castelli, surprised at the performance, carried it and read it to Galileo, who heard it with great pleasure, and conceiv ed a high esteem and friendship for the author. Upon this, Castelli proposed to Galileo, that Torricelli should come and live with him ; recommending him as the most proper person he could have, since he was the most capable of comprehend ing those sublime speculations, which his own great age, infirmities, and want of sight, prevented him from giving to the world. Galileo accepted the proposal, and Torricelli the employment, as things of all others the most advantagebus to both. Galileo was at Florence, at which place Torricelli arrived in 1641, and be gan to take down what Gallileo dictated, to regulate his papers, and to act in every respect according to his directions. But
he did not long enjoy the advantages of this situation, as Galileo died at the end of only three months. Torricelli was then about returning' to Rome ; but the Grand Duke engaged him to continue at Flo rence, making him his own mathematici an for the present, and promising him the professor's chair as soon as it should be vacant. Here he applied himself intensely to the study of mathematics, physics, and astronomy, making many improve ments, and some discoveries. Among others, he greatly improved the art of making microscopes and telescopes ; and it is generally acknowledged that he first found out the method of ascertaining the weight of the atmosphere by a proporti onate column of quicksilver, the barome ter being called from him the Torricellian tube, and Torribelliantxperiment. Great things were now expected from him, and great things would probably have been further performed by him, if he had lived ; but he died after a few days illness, in 1647, when he was but just entered the 40th year of his age. His principal work was entitled "Opera Geometries," in 4to.