and arrangement of the layers : in the former, the different
zones are parallel, while in the latter they are concentric, and
sometimes the colors of the agate are disposed in the form of
irregular clouds, veins, and spots, quite unlike those of the onyx.
Alternations of light and dark chalcedony afford the specimens
so much used in carnei. The common variety of onyx has two
opaque layers, of different colors, as black and white, dark red
and white, green and white, and some other combinations, but
the most frequent is blackish or brownish striped with white.
Some lapidaries consider the oriental variety superior to the
occidental in several points : that it has a finer, closer texture ;
that it is harder, consequently receives a finer polish ; that it is
semi-transparent, and incapable of being artificially colored ; —
but Emanuel thinks there is no essential difference between
the Indian and the German. The oriental onyx has three
layers : the upper, red, blue, or brown ; the middle, white or
pearly; and the lower, black or brown. The common variety is
frequently colored artificially, to imitate the Indian ; the
method of coloring is similar to that employed for agates,
different chemical substances being added according to the
tints required.
The onyx is occasionally found in so large masses that
small pillars are cut from it ; six of these occur in St. Peter's
Church at Rome, and one is seen in the Temple of the Magi at
Cologne. Pliny mentions thirty columns of large size in the
banquet-hall of Callistus.
This gem was a favorite material with the ancients, who
obtained it from Arabia and Persia, for cups and vases, fragments of which have been found in Roman remains. In their
wars with Mithridates, the Romans carried off, as spoils of
their victories, two thousand cups made of this stone, which
had belonged to the vanquished king. One of the most cele-
