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Page:Popular Science Monthly Volume 19.djvu/558

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The mineral appears in industry, under a still more useful form than the compressed form, as asphaltic mastic. This is made by throwing the powdered mineral into a bath of seven or eight per cent, of its weight of liquid bitumen, and mixing the whole thoroughly while it is cooked for live or six hours. The substance produced, although

PSM V19 D558 Probable formation of asphalt after erosion.jpg
Fig. 2.—Probable Formation of Asphalt after Erosion.

chemically the same, except for the difference in the relative proportions of bitumen and limestone, is physically entirely different from asphalt. It can not be pulverized by heating, but forms a paste in which the two ingredients seem to be perfectly combined, and which may be molded into desired forms. The manufacture of the mastic has become an important industry. The annual production of the French shops alone must amount to fifteen or twenty thousand tons.

In "La Nature," of April 9th, Mr. A. Woeikofen, of St. Petersburg, describes the asphaltic beds of Russia, which occur on the grand curve of the Volga, or the arc of Samara, a short distance above the city of Syzran. They are not deposited in the Jurassic formation, as are those in France, Switzerland, and Germany, but in a dolomitic limestone of the lower Carboniferous series. The mineral is rich in bitumen, of