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PRECIOUS STONES. 173
The staining is chiefly carried out at Idar and Oberstein, where also the cutting is performed. The apparatus formerly used in cutting—or more properly, grinding— was a large grindstone, about 4 feet in diameter, and 1 foot thick, driven by a water-wheel, the streams in the neighbourhood affording a plentiful supply of cheap power for the purpose. At Oberstein practically the whole population is engaged in this work. The grindstones are fixed on a horizontal axis, slightly above the floor level, and the grinders lie on their chests at full length, supported on a low rest; the Agate is held on a level with the axle of the wheel, and pressed against it; the wheel turns at about 180 revolutions per minute, so that a peripheral velocity, or cutting speed, of about 2,000 feet per minute is obtained ; in skilful hands, this enables the work to be done at a much greater rate than one would expect. The grindstones are provided with grooves of different curvatures, so that a large number of pieces can be ground to a similar form with rapidity. Although the wheels are kept wet, the occupation is a dangerous one to the health. At Birken-feld, also on the Nahe, the worker usually owns his own machinery, or it is held in a small partnership, representing about £100 capital, and there a good worker can earn £3 to £5 per week. Now most of the works at Oberstein are fitted with more modern machinery, including grinding discs rotating in a horizontal plane. The polishing is performed by women, and even children, on smaller wheels of softer material dressed with a mixture of tripolite and water.
The value of the rough material varies, according to its suitability for staining, from £5 to £250 per hundredweight (Max Bauer).
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