There are other uses besides the foregoing, but at least these are the principal ones. Let us pass on now to speak first of the shells used for carving cameos, and those employed to form articles of personal decoration. Of the quantities imported for this purpose we can obtain no reliable details. The shells come over in bags, and every now and then the City brokers announce a sale of bull's mouth, helmet shells, queen conchs, etc., but no aggregate records are kept of the numbers. To show, however, the extent of the trade in shells, here are the particulars of the sales advertised on one day in London (October 10th, 1871), by various City brokers:By Lewis and Peat— By Brooks and Faith 84 baskets, 13 bags, and 10,000 loose green snail. 230 packages and 10 tons of loose Japan ear shells. 12,000 turbos. By Donald Gray and Sons 39 cases Manila and 51 cases Bombay M.O.P. I case red shank shells. By John Griffin and Son 194 cases Bombay M.O.P. 5 tons Japan green ear. Most of the univalve shells are of the character called porcelanous, from their brittleness, translucence, and the resemblance of their fracture to that of porcelain. But this fracture, when examined by a microscope, reveals a structure of thick parallel layers, usually of a fine fibrous nature,' at right angles to the external surface. The soluble part of these shells is carbonate of lime, the particles of which are cemented together with a very minute proportion of animal mucus. The hard and compact nature of such shells, and their generally smooth surface, prevent their being cut by the ordinary tools which are available for the less hard and frangible nacreous shells; it is, therefore, necessary to treat them with emery, rotten-stone, and other substances harder than themselves. Such shells generally require rather to be polished than cut, but where it is necessary to divide them, in order to exhibit their sections, they are operated upon by means of the slicer with diamond powder. Certain description of these shells are well adapted for cameo-cutting, from their substance being made up of differently coloured layers, and also from a difference of hardness and texture in the various layers, some approaching more nearly to the nature of nacreous than of porcelanous material. The word cameo, derived from an Arab word, signifying bas-relief, was originally restricted to hard stones, such as onyx, sardonyx, etc., engraved in relief; but the name has since been extended to gems cut on shell, lava, and other substances. The good workman always carefully puts his work on the shell in such a manner that the direction of the laminæ of the central coat is longitudinal. In cameos the central layer forms the body of the relief, the inner layer being the ground, and the outer the third or superficial colour, which is sometimes used to give a varied appearance to the surface of the figure. The cameo-cutter selects from the shells which have the three layers-1. Those which have the layers strongly adherent together, for if they separate his labour is lost; 2. Those in which the middle layer is thick; 3. Those in which there is a good distinction of colour between the layers; and 4. Those in which the inner layer is of the colour suited to his purpose. The kinds now employed, and which experience has taught him are best for his purpose, are-1. The bull's mouth (Cassis rufa), which has a red inner coat, or what is called a sardonyx ground. The shell is red with several series of thick knobs, the outer lip deep yellowish red. 2. The black helmet (C. Madagascariensis), which has a blackish inner coat, or what is called an onyx ground, and shows up white upon a dark claret colour. The shell is often nearly a foot long. 3. The horned helmet (C. cornuta), white with an orange yellow ground; and 4. The queen conch (Strombus gigas), with a pink ground. This shell is about 10 inches long, aperture rose-coloured, lip extremely broad, rounded above. S. pugilis, another species, T is a turbinate shell, reddish and yellow, lip rose-coloured without and striated. The bull's mouth and black helmet are the best shells, for the horned helmet is apt to separate from the ground, or to "double," as the French workmen call it; the queen conch has the two colours seldom distinctly marked from each other, and the pink of the ground flies by exposure to the light. The red colour of the bull's mouth only extends a small distance in the mouth of the shell, becoming paler as it proceeds backward, as may be observed by the pale side generally to be seen in such red-grounded cameos. Hence, the bull's mouth affords only a single cameo large enough for a brooch, and several small pieces for shirt-studs, while the black helmet furnishes on an average about five brooches and several stud-pieces. The queen conch yields only a single good piece. Cassis flammea, about six inches long, and C. decussata and C. tuberosa, white upon a dark claret colour, are occasionally used. The bull's mouth shells are brought from India and Ceylon, the black helmets and the queen conchs from the West Indies, and all are supplied through the London market. Shell cameos, some years ago, were a good deal in fashion; and even now a well-executed, artistic Roman shell cameo is an elegant work of art. Genoa and Rome are the seats of the best work, although many common ones are cut in France. In Rome there are about 80 shellcameo cutters, and in Genoa 30, some of whom also carve in coral. The art of cameo-cutting was confined to Rome for upwards of 40 years, and to Italy until the last 26 years, at which time an Italian began cutting cameos in Paris, and now over 3000 persons are employed in that city. The black helmet, on account of the advantageous contrast of colour in the layers, produces very effective cameos, the carved figure of the white upper layer being strongly relieved by the dark, almost black, ground supplied by the second layer. The shell is first cut into pieces, the size of the required cameos, by means of diamond dust and the slitting mill, or by a blade of steel fed with emery and water. It is then carefully shaped into a square, oval, or other form on the grindstone, and the edge finished with oilstone. It is next cemented to a block of wood, which serves as a handle to be grasped by the artist while tracing out with a pencil the figure to be cut on the shell. The pencil mark is followed by a sharp point, which scratches the desired outline, and this again by delicate tools of steel wire, flattened at the end and hardened, and by files and gravers, for the removal of the superfluous portions of the white enamel. A common darning-needle, fixed in a wooden handle, forms a useful tool in this very minute and delicate species of carving. The careful manipulation necessary in this work can only be acquired by experience; the general shape must first be wrought, care being taken to leave every projection rather in excess, to be gradually reduced as the details and finish of the work are approached. To render the high parts more distinct during the process of carving they are slightly marked in black. Throughout the cutting, great caution must be observed that in removing the white thickness the dark ground is not damaged, for the natural surface of the dark layer is far superior to any that can be given artificially; indeed, should the ground be broken up at one part, it would be requisite to remove the entire scale or lamina from the |