particularly in their sacrifices to the goddess Isis. This, therefore,
may be considered one of their sacred stones, whilst there is some
analogy between the cat's-eye stones and the sacred cat of the Egyptians
which recurs so often in their hieroglyphics; it is well known that our
domestic cat is not descended from the wild cat, but from the celebrated
cat of Egypt, where history records its being "domesticated" at least
thirteen centuries B.C. From there it was taken throughout Europe, where
it appeared at least a century B.C., and was kept as a pet in the homes
of the wealthy, though certain writers, speaking of the "mouse-hunters"
of the old Romans and Greeks, state that these creatures were not the
Egyptian cat, but a carniverous, long-bodied animal, after the shape of
a weasel, called "marten," of the species the "beech" or "common" marten
(_mustela foina_), found also in Britain to-day. It is also interesting
to note that the various superstitions existing with regard to the
different varieties and colours of cats also exist in an identical
manner with the corresponding colours of the minerals known as "cat's
eye."

Several varieties of cat's-eye have already been described. Another
important variety is that of the chrysoberyl called "cymophane." This is
composed of glucina, which is glucinum oxide, or beryllia, BeO, of which
there is 19.8 per cent., and alumina, or aluminium oxide, Al_{2}O_{3},
of which there is 80.2 per cent. It has, therefore, the chemical
formula, BeO,Al_{2}O_{3}. This stone shows positive electricity when
rubbed, and, unlike the sapphires described in the last chapter, which
lose their colour when heated, this variety of chrysoberyl shows no
change in colour, and any electricity given to it, either by friction or
heat, is retained for a long time. When heated in the blowpipe alone it
remains unaltered, that is, it is not fusible, and even with microcosmic
salt it requires a considerably long and fierce heat before it yields
and fuses, and acids do not act upon it. It crystallises in the 4th
(rhombic) system, and its lustre is vitreous.

The cymophane shows a number of varieties, quite as many as the
chrysoberyl, of which it is itself a variety, and these go through the
gamut of greens, from a pale white green to the stronger green of
asparagus, and through both the grey and yellow greens to dark. It is
found in Ceylon, Moravia, the Ural Mountains, Brazil, North America,
and elsewhere. The c