TORTOISE-SHELL

TORTOISE-SHELL. The upper shell of the tortoise is composed of two dissimilar substances: that which immediately invests the back of the animal is of the bony kind, and almost as hard as stone; the outer lamina is horny, flexible, here and there transparent. It is only this last that is called tortoise-shell, and in which the beautiful colours and variegations reside. The horny shell consists of several pieces, whose seams and junctures with one another, and with the bony part underneath, are sufficiently distinguishable. The workmen split them asunder by certain instruments, and employ the elegant horn for a variety of toys and utensils, combs, sword-hilts, clock-cases, boxes, coverings for musical instruments, perspective-glasses, &c. &c.

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 affected.

Both tortoise-shell and horns may be stained of a variety of colours, by means of the colouring drugs commonly used in dyeing, and by certain metallic solutions.