erses the body of the stone on entering a diamond, and the angle at which a light-ray is totally reflected.
In
the American-cut brilliant, the rays perpendicular to the face of the
stone when faced up, passing into it, meet the back facets at angles
which successively reflect them totally until they are returned to the
face again, and pass into the atmosphere. If the perpendicular
light-rays fall upon the top side facets, they are refracted on
entering the body of the stone, and also strike the under facets at
angles which produce like results. If, however, the stone be cut too
lumpy, the sides of the upper cone, being too straight, receive the
light-rays at an angle which throws them too much to one side. On the
other hand, if the stone be cut too shallow below, the under facets
receive many of the light-rays at an angle which allows them to pass
through into the atmosphere, leaving the centre of the stone without
any play of light and dead. In either of the two latter cases, the full
reflective power of the back facets has been lost.
The
" twentieth century" is a new form of cutting lately introduced. The
number of facets is greater than in the brilliant-cut and they are
differently shaped and arranged. The first cuts of it printed showed
eighty-eight facets and proportions similar to the American brilliant,
but with an increased height from the girdle to the centre of the top,
caused by the facets replacing the table being carried to a low
pyramidal point in the centre. The stone as now cut is thinner, has but
eighty facets, and the central top facets are almost flat. A print of
the cutting is shown in Plate XV., Figs. 1, 2, and 3. It is still a
question if it will become popular. The public have not yet given it
general approval, and dealers are handling it with extreme caution,
partially on account of its greater cost. Opinions vary about it. Many
think it unsuitable for small stones, and though it increases the
surface reflection and dispersion of light-rays, some claim that the
central facets hinder the flash-light magnificence of the inner
