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CHALK,. 127 Geographic Situation. ! It abounds in the south-eastern parts of England,— extends through several provinces in France,—occupies great tracts of country in Poland and Russia,—is met with on the shores of the llaltic,—and in the islands of Zeeland and Rugen. Uses. The uses of this mineral are various. The more compact kinds are employed as building-stones, when they are used either in a rough state, or are sawn into blocks of the requisite size and shape : it is burnt into quicklime, and used for mortar in different countries; thus, nearly all the houses in London are cemented with chalk-tnor- tar * : it is also employed in great quantities in the po lishing of glass and metals, and whitening the roofs of rooms, in the state of whiting -f; in constructing moulds to cast metal in ; hy carpenters and others as a material to mark with. When perfectly purified, and mixed with ve getable colours, it forms a kind of pastil colour; thus, with litmus, turmeric, saffron, and sap-green, it forms durable colours, but vegetable colours that contain an acid, become blue when mixed with it. The Vienna white known to artists, is perfectly purified chalk. It is used ky starch-inakers and chemists to dry pecipitates on, for which * According to Smciiton, it makes as good lime as the best limestone or Warble. + tn the preparation of whiting, chalk is pounded, and diffused through water, and the liner |><irt of the sediment is then dried; hy this means, the ailiceous panicles are Rqiarated, which, hy their hardness, would scratch the surface of metallic and other substances, in the polishing of which whiting ^ Used.—V» Chtm. Dictivnurt/.