TANCREDE GRATET DE (1750-1801). A French geologist and mineralogist. The was one of the Knights of Malta when a boy, and fought a duel with and killed a brother knight, for which he was condemned to death, hut was saved in consideration of his youth. He then turned his attention to science, and visited Portugal. Spain. and Sicily. making interesting observa tions on the geological structure of the Pyrenees. He minutely described the earthquake in Cala bria in 1783, and in later years studied the Alps, where be discovered the mineral 'dolomite,' which is named after him. lie became professor in the Paris School of Alines and a member of the Institute from its formation. In 1798 lie was on the scientific staff of Bonaparte's expe dition to Egypt. Ilere he lost his health, and on the way home was left at Messina, where he was an ohject of political hatred because he had revealed in 1783 to the Grand Master of Malta the designs of the Neapolitans against. that
island. He was confined in a wretched dun geon, clothed in rags, and given only a bed of d-traw. There he was kept twenty-one months. Denied writing materials, lie made a pen from a piece of wood, and with the smoke of his lamp for ink, wrote on the margins of his Bible his Traits de philosophic and If (' mn oi re sur minerale. At the conclusion of the treaty between France and Naples. he was released and took the chair of mineralogy at the Museum of Natural History in Paris. His collections of mineralogy included numerous and valuable specimens. Besides the works men tioned above, lie wrote: Voyage crux ilex de Lipari (1783); Memoire stir le tremblement de ter•e de la Calabra (1783) : Ile/noires sur /cs ilex Ponces (1784), etc. T.ac6pede's 'Eloge historique de bubfrn.,, a is among the .11tal('ircs of the Institute for Istni.