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SPARRY GYPSUM OR SELENITE. 245 Constituent Parts. Lime, Sulphuric Acid, Water, Loss, - 100.0 Bucholz, in Gehlen’s Journ. b. v. s. 158. Geognostic Situation. It occurs principally in the first floetz gypsum forma tion, in thin layers ; less frequently in rock-salt; also in the third floetz gypsum formation ; more rarely as a con stituent part of metalliferous veins ; but in considerable quantity in that deposite known in the south of England under the name Blue or London Clay. Geographic Situation. It is not unfrequent in the blue clay in the south of England, as at Shotover Ilill, near Oxford; Newhaven, Sussex ; Isle of Shepey in the Medway ; and at Alston * n Cumberland. It occurs in the third floetz gypsum a round Paris; in veins of copper-pyrites and grey copper- ore > at Herrengrund, near Newsohl; in a vein of galena ° r lead-glance at Teschen, in Bohemia; and all over the Continent of Europe, and in other quarters of the globe U'here foliated granular gypsum occurs. N Uses. At a very early period, before the discovery of glass, selenite was used for windows; and we are told, that in time of Seneca, it was imported into Rome from S pa>n, Cyprus, Cappadocia, and even from Africa. It q 3 continued 33.9 43.9 21.0 2.1
