o the
true diamond.

Despretz at one time considered that he had discovered the process, which
consisted in his case of submitting a piece of charcoal to the action of
an electric battery, having in his mind the similar process of
electrolysis, by which water is divided up into the two gases, hydrogen
and oxygen. He obtained a microscopic deposit on the poles of the
battery, which he pronounced to be diamond dust, but which, a long time
after, was proved to be nothing but graphite in a crystallised state.
This was, however, certainly a step in the right direction.

The honour of first accomplishing the task fell to Mr Hannay, of Glasgow,
who succeeded in producing very small but comparatively soft diamonds, by
heating lampblack under great pressure, in company with one or two other
ingredients. The process was a costly one, and beyond being a great
scientific feat, the discovery led to little result.

A young French chemist, M. Henri Moissau, has since come to the front,
and the diamonds which he has produced have stood every test for the true
diamond to which they could be subjected; above all, the density of the
product is 3.5, _i.e._, that of the diamond, that of graphite reaching 2
only.

He recognised that in all diamonds which he had consumed--and he consumed
some L150 worth in order to assure himself of the fact--there were always
traces of iron in their composition. He saw that iron in fusion, like
other metals, always dissolves a certain quantity of carbon. Might it not
be that molten iron, cooling in the presence of carbon, deep in volcanic
depths where there was little scope for the iron to expand in assuming
the solid form, would exert such tremendous pressure upon the particles
of carbon which it absorbed, that these would assume the crystalline
state?

He packed a cylinder of soft iron with the carbon of sugar, and placed
the whole in a crucible filled with molten iron, which was raised to a
temperature of 3000 deg. by means of an electric furnace. The soft cylinder
melted, and dissolved a large portion of the carbon. The crucible was
thrown into water, and a mass of solid iron was formed. It was allowed
further to cool in the open air, but the expansion which the iron would
have undergone on cooling, was checked by the crucible which contained
it. The result was a tremendous pressure, during which the carbon, which
was still dissolved, was crystallised into minute diamonds.

These showed themselves