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BORT CARBONS, ETC.
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325
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markets
of the world, owing to the wide range of quality in the unassorted lots
at the mines and the varied assortments made to suit the demand of
different countries and also to the fact that the character of the
material is speculative. It is also necessary to ascertain the
exchange value of the milreis at the time, when quotations are made in
Brazilian money, as there have been great variations in the value of
the milreis.
Artificial Diamonds.
There
have been many attempts to make diamonds. The difficult problems
involved have excited the desire of scientists to solve them and the
great value of the gem has been an incentive to hundreds who
experimented in the hope that they might learn how to turn one of the
common elements of the earth into costly jewels. Stimulus was given to
these endeavors by the discovery of the diamond chimneys of Africa.
Occurring there in the mother-rock, it was thought that clues might be
obtained to the processes by which Nature accomplished the
crystallization of carbon, but so far, of all the theories evolved by
observation and experiment, those which were in any degree carried to
a successful issue, demonstrated more forcibly in practice the
insufficiency of man's appliances, than his ability to compete with
Nature.
Carbon,
unlike many elements, occurs in Nature un-combined with others and in
three forms; as graphite, carbonado and diamond. In combination with
others, it appears as a solid in minerals, a semi-solid as in
vegetation, a liquid as in earth-oils, and a gas as in carbonic acid.
At a high temperature it vaporizes without
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