TORTOISE-shell, the shell, or rather scales, of the
testaceous animal called a tortoise; used in inlaying, and
in various other works, as for snuff-boxes, combs, &c.
Mr Catesby observes, that the hard strong covering
which incloses all sorts of tortoises, is very improperly
called a shell; being of a perfect bony texture; but
covered on the outside with scales, or rather plates, of a
horny substance; which are what the workmen call
tortoise-shell.
There are two general kinds of tortoises, viz. the
land and sea tortoise, testudo terrestris and marina. The
sea-tortoise, again, is of several kinds; but it is the caret,
or testudo imbricata of Linnaeus, alone which furnishes
that beautiful shell so much admired in Europe.
The shell of the caretta, or hawk-bill tortoise, is
thick; and consists of two parts, the upper, which cov-
ers the back, and the lower the belly: the two are
joined together at the sides by strong ligaments, which
yet allow of a little motion. In the fore-part is an aper-
ture for the head and fore-legs, and behind for the
hind-legs and tail. It is the under shell alone that is
used: to separate it, they make a little fire beneath it,
and as soon as ever it is warm, the under shell becomes
easily separable with a point of a knife, and is taken off
in lamina or leaves.
The whole spoils of the caret consist in 13 leaves or
scales, eight of them flat, and five a little bent. Of the
flat ones, there are four large ones, sometimes a foot
long, and seven inches broad. The best tortoise-shell
is thick, clear, transparent, of the colour of antimony,
sprinkled with brown and white. When used in mar-
quetry, &c. the workmen give it what colour they
please by means of coloured leaves, which they put un-
derneath it.
Working and joining of TORTOISE-shell.—Tortoise-
shell and horn become soft in a moderate heat, as that
of boiling water, so as to be pressed, in a mould, into
any form, the shell or horn being previously cut into
plates of a proper size. Plumier informs us, in his Art
de Tourner, that two plates are likewise united into one
by heating and pressing them; the edges being thoroughly
cleaned, and made to fit close to one another. The
tortoise-shell is conveniently heated for this purpose by
applying a hot iron above and beneath the juncture,
with the interposition of a wet cloth to prevent the shell
from being scorched by the irons: these irons should be
pretty thick, that they may not lose their heat before
the union is effected. Both tortoise-shell and horns may
be stained of a variety of colours, by means of the col-
ouring drugs commonly used in dyeing, and by certain
metallic solutions.