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202 PRECIOUS STONES.
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some traces of organic matter, and about 1 part to the 100 of oxide of iron.
Coral
possesses a very interesting property, which, beyond doubt, contributed
to elevate it to the exceptional rank that it has occupied in
medicine, even to the nineteenth century. Certain persons cannot wear
against their skin any objects of coral without discolouring them, and
this phenomenon is general among all invalids. The ancients asserted
that if a person wearing a necklace of coral was on the verge
of an illness, the coral showed discoloration before the least
consciousness was felt of the approaching malady.
Naturalists
and chemists have of course inquired what is the nature of this
singular colouring matter that is so exceedingly impressionable? So
far, the only colouring substance which chemistry has detected in
coral is oxide of iron, one of the most fixed in nature, and one which,
under the circumstances, cannot enter into new and colourless
combinations; consequently the problem has not yet reached a solution.
AMBER.
Amber
has been known from earliest antiquity. The celebrated founder of the
Ionian school of philosophy, Thales, who lived 600 years before our
era, speaks of the property which, above all,
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