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PRECIOUS STONES.
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slitting
with a metal disc, as described in dealing with the slitting of
Diamonds, powdered Diamond mixed with olive oil being used to make the
disc cut the harder stones, while for the softer, Emery powder and
water may be applied to the somewhat roughened edge. The natives of
Ceylon used a fine wire strung on a bow and dressed with the cutting
powder to slit precious stones.
In cutting stones en cabochon the
operator holds the little handle on which the gem is mounted and keeps
it constantly moving in position, especially as the work nears
completion, so as to give a smoothly-rounded form. The smaller Garnets
are fashioned on a fine sandstone disc, dressed with Emery powder and
olive oil.
The
cutting of Agates, Amethyst, Opal, Topaz, Jasper and other stones which
are relatively softer and more plentiful, is largely done at
Birkenfeld, on the Nahe, lying to the west of the Rhine, close to the
French frontier. Here may yet be seen many of the older methods still
in use. The work is carried on in small huts adjacent to streams which
provide the power to drive the water-wheels, which in turn drive three
or four grindstones of about four feet in diameter ; the grindstones
are so placed that their axles are only a foot above the floor level,
while the lowest part of the stone dips into the stream below, and thus
the stone is kept constantly wet. The workmen lie prone on low wooden
supports, and hold their work a little above the level of the floor. In
spite of the stones being kept moist, a great deal of dust, consisting
of sharp, angular mineral fragments, is thrown off, and consequently
inhaled, giving rise to great irritation in the lungs, and paving the
way for consumption, which, having once been introduced,
P.S.
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