it should be resumed, in order that Italy may not lose an industry which belongs to her, and from which she may derive profit.
XXV.
SHELLS.
Shells must be permitted to enter in a small degree into this treatise, as some of them are used in making jewels and ornaments.
Such are those known by the name of cama, cassis rufa, and cyprea, which
are upright, thick, and generally composed of strata of varied colours
and different degrees of hardness. Each of these is composed of many
very thin lamina, which are perpendicular to the level of the principal
stratum, which is the hardest, and perfectly resembles enamel ; every
lamen consists of a series of prismatic, lengthened cells, adhering by
their longest side.
It
can easily be perceived, from this short description, that some shells
can have parallel strata of different colours distinctly separated, and
that, therefore, at a cheaper rate, they can take the place of the
onyx and agate used by cameo workers. In fact, they make very delicate
carnei of them, because cut with a steel graving tool.
It
is to be regretted that the art of carving shell carnei, which was, it
may be said, peculiar to Rome, should be now so little valued. This
must be caused
