BAILLY, JEAN-SYLVAIN

born Sept. 15, 1736, Paris died Nov. 12, 1793, Paris French astronomer noted for his computation of an orbit for Halley's Comet (1759) and for his studies of the four satellites of Jupiter then known. He was also a statesman who took part in the revolutionary events of his age. Bailly began his study of Halley's Comet in 1759. One year later he established an observatory where he could undertake observations of Jupiter's satellites. He was elected to the Acadmie des Sciences in 1763. His major works include Essai sur la thorie des satellites de Jupiter (1766; Essay on the Theory of Jupiter's Satellites) and Mmoires sur les ingalits de la lumire des satellites de Jupiter (1771; Memoirs on the Uneven Illumination of Jupiter's Satellites). The French Revolution interrupted his studies. Elected deputy from Paris to the States General, he was chosen president of the third estate on May 5, 1789, and led the famous proceedings in the Tennis Court on June 20. He was proclaimed the first mayor of Paris on July 15, 1789. He was reelected mayor in August 1790 but lost popularity, particularly after his order to the national guard to disperse a riotous crowd led to the massacre of the Champ de Mars on July 17, 1791. Bailly retired on Nov. 16, 1791, and went to Nantes in July 1792, where he composed Mmoires d'un tmoin de la Rvolution (Memoirs of a Witness of the Revolution), an incomplete narrative of the extraordinary events of his public life. Late in 1793 Bailly went to Melun to join his friend Pierre-Simon Laplace, but was recognized, arrested, and taken before the revolutionary tribunal at Paris on November 10. He was subsequently guillotined.