the history of fossils, a genus of crystals, the figures of which are influenced by an admixture of some particles of tin.

The cassiteria are of two kinds: the whitish pellucid cassiterion, and the brown cassiterion; the first is a tolerably bright and pellucid crystal, and seldom subject to the common blemishes of crystal: It is of a perfect and regular form, in the figure of a quadrilateral pyramid, and is found in Devonshire and Cornwall principally. The brown cassiterion is like the former in figure: It is of a very smooth and glossy surface, and is also found in great plenty in Devonshire and Cornwall.