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.232 MINERAL REPOSITORIES. branches at their ends and bottom, but lefs fre quently at the bottom than at the ends. 3. The mafs of the greater number of veins is feparated from the rock through which it paffes, by a very delicate feam ; but in others this is not the cafe. Sometimes the fides of the vein are coated with a clayey fubftance, which is denominated Bejleg by the German miners; but this does not always continue throughout the whole extent of the vein in which it occurs. In other cafes the fubftance of the vein is intimately mixed with its walls. 4. Veins are compofed either of earthy maf- fes, as clay or loam, or rocks, as granite, clay- flate, alum-flate, porphyry, fandftone-conglomerate, fandftone, floetz-Iimeftone, coal, bafalt, wacke, greenftone, pitchftone, porphyry-flate, or ores of different kinds. The ftony materials of which many veins are compofed, have been formed either on the fpot, or have been brought, generally in the form of fragments, ready-formed, from a diftance. In the one cafe, they are either fragments of the walls of the vein, or fragments from older parts of the fame vein, or fand, gravel, rolled-maffes, or fandftone : in the other, they are mountain- rocks, or fimple foflils of different kinds, as calc- fpar, heavy-fpar, brown-fpar, fluor-fpar, zeolite, jafper, opal, agate, chalcedony, quartz, hornftone, &c. There is fcarcely any fpecies of ore that does not occur in veins. It is alfo well known that ge nerally