HAUY, RENE-JUST, ABBE, a distinguished French mineralogist, was born February 28, 1743, at St. Just, in the present department of Oise. He commenced his studies at the college of Navarre, to which college be was appointed professor in 1764, and subsequently also to that of the Cardinal Le 3loine. His attention was first drawn to the subject of mineralogy by attending the lectures of M. Dauben ton, but the accidental fracture of a beautiful specimen belonging to his friend 3L France de Croisaet is said to have led him to the discovery of the geometrical law of crystallisation. Haiiy was anxiously em ployed in collecting the scattered fragments of the crystal which he had broken, when M. Croisset, whom the accident had rendered almost inconsolable, desired he would not give himself that trouble, and directed a domestic to remove the pieces, which, in his own opinion, were no huger of any value. But Haiiy, who regarded them with extreme attention, requested permission to remove them himself, remarking that the conformity of the superposed plates of crystalline matter with the planes of the central prism or nucleus had revealed to him a secret which he wished more fully to explore. From this moment he applied himself sedulously to the development of the truth which his genius bad detected, and his efforts were rewarded with the success they merited. He was the first to show that the structure of crystalline substances was regulated by laws as invariable as those to which organised bodies are subjected, and thus crystallo graphy for the first time assumed the character of a regular science. His theory rests upon the supposition that all the crystallioe forms belonging to any single species of mineral are derivable from some one simple form which may be regarded as the type of the species; it likewise supposes that the angles at which the planes of crystals can be inclined to each other are confined within certain limits, an erroneous supposition which may probably be attributed to the imper fection of the instrumenta employed to measure them. In compliance
with the request of Messrs. Danbenton and Laplace, Hedy communi cated the result of his researches to the Royal Academy, and was elected a member of that society in 1783.
During the Revolution be was thrown into prison for refusing to take the oath of obedience required of the priest, but the exertions of Geoffrey Saint-Hilaire, one of his pupils, and the remark of a citizen, that "it were better to spare a recusant priest, than to put to death a quiet man of lettere," obtained hie release, and probably saved his life. In 1791 he was appointed conserver of the mineralogical collets. Howl of the School of Mines, and the following year be received the appointment of secretary to the commission of weights and measures. Under the consulship of Napoleon he became professor of mineralogy at the Museum of Natural History, and professor of the Faculty of Sciences at the Academy of Paris. Flatly died at Paris, June 3, 1822. Besides numerous memoirs upon mineralogy and electricity, inserted in the 'Journsl des Mines ' and the 'Annals of the Museum of Natural History,' he has left the following works An Essay on the Structure of Crystals,' 1 vol., 1784 ; 'Exposition of the Theory of Electricity and Magnetism,' 1 vol.; ' Treatise on Mineralogy,' 4 vols., 1822; ' Treatise on Physics,' 2 vols., 1821; ' Treatise on Crystallography,' 2 vole., 1822; and some others.