once dry, remain constant in weight. But the carat is not of absolutely the same significance in all countries.
The
European Diamond trade is now centred in Antwerp, and Amsterdam ; some
factories having been also established in the United States of America.
In Diamond-cutting the first rough formation is termed "brutage"; the
rough stones being then embedded in liquid Aluminium, within moulds.
Having become thus fixed when cool, they are taken from the moulds, and
cloven with a circular saw, into the cutting edge of which some diamond
dust with oil is forced ; next one stone is rubbed against another
until the required formation is achieved; each stone is first fixed in
cement for this purpose,—the cement being then set by plunging it into
cold water. The " diamond-dust " which is produced by thus rubbing the
two stones together falls into a copper box, called an "egrisoir,"
placed immediately below the diamonds which are being worked. This dust
is carefully preserved. Finally a stone is polished into facets, on a
revolving disc of soft steel, rotating horizontally at a speed of some
three thousand revolutions to the minute. In olden times Diamond
cutters contented themselves with thus producing as large a number as
possible of small facets on the surface of a stone. But since then it
has become manifest that for obtaining the best results, and the most
sparkling lustre, a Diamond must be cut into a regular form, so that
one facet-surface may reflect on another, thereby bringing out the
hidden light, and beauty of the stone. Because the molten metal within
a mass of which the stones are fixed for polishing is composed mainly
of lead, therefore the exceedingly rapid revolution of the wheel makes
this
