Leverrier, Urban Jean Joseph (1811-77), the greatest French astronomer of the 19th century, was a native of St. Lo, Normandy. After a brilliant career at the Ecole Polytechnique he obtained some reputation as a chemist, but was induced to transfer his attention to the study of astronomy in 1837 by the offer of the post of teacher at the Polytechnic. He soon attracted the attention of Arago, and in 1843 published Tables de Mercure. In 1846 he was elected to the Academie des Sciences, and in the same year, as the result of minute investigations, he indicated the spot where an unknown planet would be found. A few days later Neptune was discovered within a degree of the place. John Couch Adams, of Cambridge, had reached a similar result independently. The Royal Astronomical Society awarded a medal to both astronomers for the discovery, and Leverrier afterwards received the Copley Medal, the Legion of Honour, and many foreign decorations. He also became tutor to the Comte de Paris, and professor in the Faculte des Sciences. In 1849 he entered the Assembly as a Republican, but was opposed to the Socialists. Nevertheless, Napoleon III. made him a senator, and appointed him Inspector-General of Public Instruction. In 1854 he succeeded Arago as director of the Paris Observatory, from which he was obliged to retire in 1870 on account of the outcry which his reforms excited. He was reinstated by Thiers with limited powers in 1873, and devoted the rest of his life to the revision of planetary theories, a comparison of results with observations, and the construction of illustrative tables.