ia,
Burma, Ceylon, South Africa, America, and in many other places, having a
wide distribution.

_The Ruby._

In the dichroscope the ruby shows two images, one square of a violet
red, the second square being a truer and a paler red. It may be
subjected to strong heat, when it changes its colour to a sooty or dirty
slate, this varying with the locality in which the stone is found, and
the manner in which the heat is applied. But as it cools it becomes
paler and greener, till it slowly enrichens; the green first becomes
broken, then warmer, redder, and finally assumes its original beautiful
blood red. This method of heating is sometimes used as a test, but it is
a test which often means the complete ruin of a stone which is not
genuine. Another characteristic which, in the eyes of the expert,
invariably isolates a real from an artificial ruby is its curious mild
brilliance, which as yet has not been reproduced by any scientific
method in paste or any other material, but perhaps the safest test of
all is the crystalline structure, which identical structure appears in
no other stone, though it is possible, by heating alumina coloured with
oxide of iron and perhaps also a trace of oxide of chromium to a very
high temperature for a considerable time, and then cooling very slowly,
to obtain a ruby which is nearly the same in its structure as the real
gem; its specific gravity and hardness may perhaps be to standard, and
when properly cut, its brilliance would deceive all but an expert. And
as in some real rubies there are found slight hollows corresponding or
analogous to the bubbles found in melted glass, it becomes a matter of
great difficulty to distinguish the real from the imitation by such
tests as hardness, specific gravity, dichroism, and the like, so that in
such a case, short of risking the ruin of the stone, ordinary persons
are unable to apply any convincing tests. Therefore, only the expert can
decide, by his appreciation of the delicate shade of difference in the
light of a true ruby and that of an excellent imitation, and by the
distribution of the colour, which--however experienced the chemist may
be, or with what care the colouring matter may have been incorporated in
the mass--has been found impossible of distribution throughout the body
of an artificial stone so perfectly and in the same manner and direction
as nature herself distributes it in the genuine. This alone, even in the
closest imitations, is c