the East Indies. The Hydrophanous Opal, or Oculus Mundi, is
so named because of an internal luminous spot which changes its
position according to the direction in which this stone is held towards
the light. The phenomenon of such stones becoming transparent in water
is thought to be occasioned by that fluid soaking through their whole
substance, in the same manner as the transparency of paper is
occasioned by immersing it in oil. When taken from the water these
stones, as they dry, become again opaque. Care should be observed not
to immerse them in any but pure water, and to take them out therefrom
as soon as they have acquired their full transparency ; otherwise the
pores will shortly become filled with earthy particles ; when the
stones will cease to exhibit this peculiar property, and will always
afterwards remain opaque.
(Reverting for a moment to the Rock Crystal, it is interesting to know that a specially choice, valuable Crystal casket, wThich
the late Queen Victoria possessed, was dedicated by her to enshrining
the small Bible which General Gordon carried invariably with him
through all his campaigns, and which was found still in his precious
keeping at the time of his devoted death.)
The
Etematitis already referred to, or " Lapis Sanguineus," is a hard,
solid, heavy stone comprising particles of iron, disposed like needles,
it being of a reddish-brown colour, and becoming red as blood according
as it is reduced to powder. It " is brought from many places, there not
being any iron mines wherein it is not found." " The best, and most
esteem'd is that from Spain." " Chuse such as is of a brownish-red,
weighty, solid, and smooth; it is astringent, and is called Hsema-titis
from the Greek word ' aima,'—' blood,' because,
