HAÜY (René-Just). EXPOSITION RAISONNEE DE LA THEORIE DE L'ELECTRICITE et du magnétisme, d'après les principes de M. Æpinus. Paris, Veuve Desaint, 1787. In-8 of 27-[5]-238 pages, spotted basane, smooth spine decorated (later binding). First edition illustrated with 4 folding plates. 2 table leaves missing. Bound in the sequel by the same author: - ESSAI D'UNE THEORIE SUR LA STRUCTURE DES CRYSTAUX, applied to several kinds of crystallised substances. Paris, Gogué & Née de La Rochelle, 1784. [8]-236 pages. Rare ORIGINAL EDITION of the founding book of the science of crystallography, in which Hauÿ explains the law that bears his name. It is illustrated with 8 folding plates engraved by Sellier after drawings by Fossier. Some foxing but otherwise a very good copy. (Horblit n°47).