Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/361

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The Abbé Haüy in his “Traité de Minéralogie” assigned the cube to the oxyd of tin as its primitive form, because he thought he “ perceived the natural joints parallel with the faces of that solid, although they were not sufficiently determinate to remove all doubt.” This opinion was combated by Mr. Day in a paper on this substance, published in an early volume of the Philosophical Magazine, in which he assumed as its primitive crystal an octahedron composed of the two quadrilateral pyramids commonly seen