ducing
a lantern slide of microscopic diamonds which he had made in the same
way previously, for it takes a fortnight to separate them from the
iron and other substances in which they are imbedded.
The
scientific principle upon which this experiment rests, according to Sir
William Crookes, is that iron dissolves carbon, and it increases in
volume as it passes from the liquid to the solid state. Authorities
differ somewhat as to the exact moment when molten iron expands in
cooling, but it is the generally accepted theory that expansion takes
place at the moment of solidification. It is also a well-known fact
that shrinkage or contraction takes place as the solidified metal
cools. It is therefore possible to obtain enormous pressure in the
molten center of a casting by the contraction of the outer shell which
has been rapidly cooled and the expansion of the inner mass just as it
begins to solidify. This process supplies the two factors necessary for
the crystallization of the diamond—heat and pressure.
Of
the early attempts to make synthetic diamonds the most successful was
that of Henri Moissan, a Frenchman, who, after patient and careful
experimenting succeeded in 1896 in obtaining minute particles of
diamonds. He very carefully investigated the scheme that Nature
employed in making her diamonds and he found that she did so by heating
carbon to a very high temperature and cooling it suddenly under
enormous pressure. Swedish iron was melted in the presence of sugar
carbon in an electric furnace at a temperature which, seldom exceeded
two thousand degrees Centigrade. When the iron was saturated with
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