CAVENDISH, HENRY, a distinguished philosopher of the 18th c., son of lord Charles Cavendish, and nephew of the third duke of Devonshire, was born at Nice, Oct. 10, 1731. He studied at Cambridge, and devoted his whole life to scientific investigations. The large fortune which was bequeathed to him by an uncle, enabled him to follow uninterruptedly his favorite pursuits. Ile almost secluded himself from the world, and was so averse to meet with strangers, that he had his library—a magnificent one—built at a distance from his house, so that he tnight not encounter persons coming to consult it; and his female domestic servants had orders to keep out of his sight, on pain of dis missal. Ills dinner he ordered daily by a note placed on the hall table. Reified, unmar ried, Feb., 1810, leaving considerably more than a million sterling to his relatives. As a. philosopher, C. is entitled to the highest rank. To him it may almost be said we owe
the foundation of pneumatic chemistry, for prior to his time it had hardly an existence. In 1760, he discovered the extreme levity of inflammable air, now known as hydrogen gas—a discovery which led to balloon experiments, and projects for atrial navigation; and later, he ascertained that water resulted from the union of two gases—a discovery, however, to which Watt (q.v.) is supposed to have an equal claim. The accuracy and completeness of 0.'s processes are remarkable. So high an authority as sir Humphry Davy declared, that they "were all of a finished nature. and though many of them were performed in the very infancy of chemical science, yet their accuracy and their beauty have remained unimpired amidst the progress of discovery." C. also wrote papers on electricity, astronomical instruments, etc.