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A celebrated French astronomer; born at St. Lo, March 11, 1811; died at Paris, Sept. 23, 1877. Till 1837 his studies were wholly in the department of chemistry; in that year he was appointed teacher of astronomy in the Polytechnic School. In 1839 he attained rank among the foremost astronomers by two memoirs presented to the Academy on "Secular Perturbations of the Planetary System". He then studied the movements of Mercury and Uranus, and was led to infer the existence of a planet beyond Uranus: the inference was proved true by the finding of the hypothetical planet (Neptune) by Galle. His theories and tables of the several planets are given in the "Annals of the Paris Observatory".