The perfectly white solution of the scales of the bleak (Leuciscus alburnus), a fish indigenous to the rivers of France, is now used largely for the manufacture of artificial pearls. The solution or guanine is a mucus which lubricates the scales of the fish. It coagulates by heat to a thick, white deposit, and is obtained by carefully scraping the fish over a shallow tub containing fresh water. Care is taken not to scale the black or dorsal part, as these scales are yellow, while the white scales only possess value. The material is received on a horsehair sieve. The first water, mixed with a little blood, is thrown away. The scales are then washed and pressed, when the mucus or essence (guanine) sinks to the bottom of the tub and appears as a very brilliant bluewhite oily mass. It takes 40,000 fish to furnish two pounds of the material. The fishermen seal it in tin boxes with ammonia, and in this condition send it to Paris. If a drop of the essence be taken up by a straw and let fall upon water, it floats, giving forth the most brilliant colours. Glass bulbs, in the shape of pearls, lined with this substance, imitate the real gems with remarkable closeness.

CHAPTER X.

INDUSTRIAL AND MANUFACTURING USES OF SHELLS.

Composition of shells-Variety of forms and colours-Various economic uses to which they are put-Extensive commerce in shells-Shell cameos-The cowry shells-Their various uses, as currency, for decoration, etc.-Shells worn for personal ornament-Wampum or treaty belts of shells-Shells as studies of design-British commerce in shells.

SHELLS, from their variety of structure and colour, and their singular beauty, have always formed a fruitful theme of description for the writer and the poet. The works of most of our best authors teem with lovely passages, many of which must occur to the memory of any general reader.

"Their exquisite, fragile, and beautiful forms

Are nursed by the ocean and rocked by the storms."

By young and old, savage and civilized, shells are alike admired and coveted, either for personal decoration, for the cabinet of the collector and the naturalist, or as simple ornaments in a room.

The uses to which shells are applied are more extensive than is generally supposed. The trade is growing year by year into greater importance; and there is ample scope yet for its extension with profit and advantage, alike to the merchant and importer, to the manufacturer and vendor, and to the general public who are the purchasers.

To understand the composition of shells, a little preliminary scientific definition must be given. It has been observed that shells may be regarded as epidermal in their character, being formed upon the surface of a filmy cloaklike organ, called a mantle, which answers to the true skin of other animals. A slimy juice, consisting of a membranaceous tissue, consolidated by an admixture of carbonate of lime, exudes from the glands of this important organ, and, thickening in successive layers, becomes hardened and moulded on the body, at first simple and unadorned, but subsequently embellished according to the taste or inclination of the occupant. Each shell is therefore composed of animal and calcareous matter; the first constitutes a membranaceous basis, which is equally curious and beautiful, being either formed of cells with hexagonal walls, or else of laminæ, more or less wrinkled, like morocco leather. Shells which are always concealed by the mantle are colourless; and those which are covered by the mantlelobes, when the animal expands, acquire a glazed or enamelled surface, like the cowries; when the shell is deeply immersed in the foot of the animal it becomes partly glazed, as in Cymba. In all other shells there is an outer layer of gelatinous matter forming what is called the epidermis, although it is sometimes very thin and transparent.

Woodward well remarks that the forms and colours of shells (as of other natural objects) answer some particular purpose, or obey some general law; but besides this there is much that seems specially intended for our study and calculated to call forth enlightened admiration. Thus the tints of many shells are concealed during life by a dull external coat, and the pearly halls of the nautilus are seen by no other eyes than ours.

The variety in the figure, colour, and characters of sea shells is almost infinite. The most beautiful come from the Pacific and Australian coasts. The sun, by the great heat that it throws on the seas near the equator, would seem to have some effect in heightening the colours of shells produced in tropical zones, and the nature of the food of the animals probably gives them a lustre and a brilliancy which are wanting in those of colder latitudes.

It is impossible to enumerate all the purposes to which shells are applied, but some few may be specified.

The shells of Strombus, Triton, Dolium, Fusus, Murex, and Buccinum are used for fog-horns, trumpets, lamps, vases, and ornamental borders in flower gardens. Those of Busycon, Sycotypus, Mactra, etc., by Indians in the manufacture of implements. Shells of species of Mactra for ladles, scoops, and spoons, by fishermen.

Those of Tridacna for vases, fountains, and in the manufacture of handles and carvings. The shells of Pecten, Haliotis, Dentalium, Mercenaria, etc., by the Indians for trimmings and ornaments. The scallop or palmer's shell (Pecten jacobæus) was used as a decoration of honour. Other Pectens are used in making pincushions and purses. The chank shell is used in the manufacture of Hindoo bangles, and in polishing or glazing cloth. The painter's mussel (Unio pictorum) is used to hold gold and silver colours. The shells of Placuna placenta are employed in China as a substitute for glass. Cytherea lusoria, the painted shell of the Japanese, with pretty designs on it, is used for playing a game. The cowries serve for currency in India and in the African trade, and for trimmings to various trappings. The shells of Mercenaria violacea, Purpura lapillus, and Buccinum undatum are used by the Indians of the eastern coast of America in the manufacture of their native money, and

for modern wampum or shell beads for the Indian trade. The hyqua or Dentalium shells are employed in a similar manner by the Indians of the Pacific coast. The shells of Cypræa, Rotella, Oliva, Turretella, Phasianella (Venetian shells), etc., are mounted as buttons and jewellery. Composition shellwork for book-covers and frames is made by glueing various shells in mosaics. Calcined shells are used by dentrifice and porcelain makers. Cuttle-fish bone, from Sepia officinalis, has various uses. The opercula of some molluscs are used as "eye-stones," and polished and set for jewellery.

In considering the manufacturing and useful applications of shells, they might be conveniently ranged under the following groups-1. The nacreous shells used for making pearl buttons and other useful and ornamental articles. 2. The pearly and iridescent shells, for ornamenting papier-mâché work, making card-cases, folios, jewel-cases, etc. 3. Various small shells used for making shell flowers and different fancy articles of grouped shells, and for ladies' bracelets, head-dresses, etc. 4. The shells used for carving cameos to set in brooches, bracelets, necklaces, scarf-pins, for studs and sleeve-links, and other articles of personal decoration. 5. Shells used for spoons, drinking-vessels, lamps, handles for knives, and other purposes of domestic economy; for snuff-boxes, pipes, and such like curiosities. 6. For making the purest kind of lime when calcined; for manure, in the form of shell sand and shell marl; and for making pottery-ware and a glaze or enamel, when crushed. 7. Shells are largely used for small monetary payments in North America, India, and Africa, and also as counters in games of chance. Lastly, they serve as studies of design, form, and colour for the sculptor, painter, and art manufacturer.