Astronomer, born Saint-Lô, France, 1811; died Paris, France, 1877. He was successively professor at the Ecole Polytechnique, the College Stanislas, and the University of Paris. In 1839 he published a calculation of the planetary orbits from 100,000 B.C. to A.D. 100,000, proving the stability of the solar system, but his great triumph was his theoretical calculation of the exact spot where the hitherto undiscovered planet Neptune was to be found, as was done under his direction by Galle at Berlin, September 23, 1846. He also suggested the existence of a planet between Mercury and the sun. Between 1858,1877 he compiled most valuable tables of the movements of the solar system. In 1853 he succeeded Arago as director of the Paris Observatory. He founded the International Meteorological Institute, and organized the French weather bureau service. He was a fervent Catholic and did not hesitate to condemn publicly the materialistic and sceptical tendencies of so many modern scholars.