to
yield distinct crystals of chrysoberyl. It is probable that in Nature
the formation of gem-stones has occurred in the presence of water, and
under very great pressure continued for a long time. Indeed, it may be
concluded that the agency of a very high temperature has not been
generally at work, but that the important elements in the production of
natural crystals have been time, mass, and pressure.
Chemists
have devoted much time and skill to devising methods for producing
diamonds. These methods have rarely been successful, but M. Henri
Moissan has really made a number of small— very small—diamonds by
causing carbon to dissolve in molten iron at the high temperature of
the electric furnace and then, by sudden cooling of the metallic mass,
causing the formation of a rigid shell and so producing great pressure
in the interior : the iron mass treated with acid left a residue
containing small diamond crystals : by slow cooling graphite only was
formed.
