SHELLS, Economical uses of. Shells are applied to several usefu purposes, and to still more of an ornamental character. Some of their furnish dyes and pigments. The purpune contain an intense purph dye, in a few drops of liquid enclosed within a vein or sac in the fish The murex yields various shades of purple and crimson. The cutile fish supplies the well-known sepia, of intense blackness. The beautifu substance called mother-of-pcurl is described under PEARL FISHERY The large proportion of lime in many shells renders thorn useful it making cement, and also as a fertiliser in agriculture. Shell-sand, pro. duced by the natural crumbling of shells on the seashore, given moderate fertility to many spots otherwise barren. Ground cockle are mussel shells are sometimes used as a covering for gravel walks. ewere shells, inexhaustibly abundant on the shores of Asia and Africa, are used in India for the purposes of money, at an average value of about 200 for an English penny. The same cowries may be converted into I glaze for earthenware, and an enamel for clock-faces. A calcareous spongy plate found in the cuttle.fish is used by workmen as a substitute for emery-paper or sand-paper. The conch shell is in some countries used as a horn or trumpet ; as in the West Indies, where on some plantations the negroes are summoned to work by a ' conch-blow." The oanotis luta an iridescent surface which fits it for use as a substitute [or mother-of-pearl In inlaid work. The helmet shell supplies pieces arge enough for umbrella-handles; and thinner portions as ornaments for workboxes and other trinkets. Smoked films from oyster-shells
are used for large coat-buttons. The clang shells, often of very large size, aro used in Roman Catholic countries as receptacles for holy-water ; while some, perfectly white, are cut up for firm-rings and other mita. inents. The fibres with which many kinds of aliell-fish attach them selves to rocks, such as those of the piano, are fine and strong enough to be worked up in the manner of Bilk. The chank shells of India are cut up into bangles, armlets, 'bracelets, anklets, finger-rings, toe-rings, fie., sometimes carved and gilt, or otherwise decorated. The fishery of cliank shells, off Ceylon, is a very valuable one; seeing that some of the choice specimens are valued at their weight in gold. [CEYLON, in GEoo. Div.] Shell cameos are noticed under CAMEO.
Considered as a working material, all shell is placed in one or other of two categories, porcelanous or nacreous. The poreelanous shells contain much lime and little animal matter ; they are brittle, translu cent, smooth, and not easily cut, and much resemble the enamel of teeth. They can only be worked on the lapidary method, with small grinding wheels. The nacreous shells, partaking of the nature of mother-of-pearl, contain less lime and more animal matter ; they arc tougher, softer, and iridescent ; they may be easily sawn, scraped, and filed ; and can then be polished with sand or pumice and water. [LAPIDARY Woes.)