Hailly

Hailly, RENÉ JUST, a French mineralogist, was born at St Just, department Oise, 28th February 1743, studied for the church, and took priest's orders. His attention was first turned to botany, and it was not until middle life that he commenced the study of mineralogy. He is the discoverer of the geometrical law of crystallisation, and he also considerably enriched our knowledge of pyro-electricity. After occupying several important posts, such as commissioner of weights and measures, curator of the cabinet of mines, and professor of mineralogy, he died on 3d June 1822. His most important works, besides an essay on crystals and a treatise on electricity, are Traité de Minéralogie (2 vols. 1801), Traité Élémentaire de Physique (2 vols. 1803), Traité des Caractères Physiques des Pierres Précieuses (1817), and Traité de Cristallographie (2 vols. 1822).—His brother VALENTIN HAÏY (1745–1822) devoted his life to the education of the Blind (q.v.). He wrote Essai sur l'Éducation des Aveugles (1786).