"They are the ordinary conch-shell. In each one there is material for only a single cameo, large or small. The available part is sawed out by persons employed for that work, who also shape the cameo by grinding the piece upon a grindstone, making it square or oval as desired; then it is ready to be handed over to the artist. The cutter fastens the shell into a small block of wood, of a size convenient for grasping firmly with the left hand. He then draws the outline of the figure he wishes to put upon it with a pencil. When the work is outlined upon the white surface, he begins to scratch the line with a fine steel needle, following his pencil mark very carefully. The artist I saw at work inspected his scratches with a magnifying glass at almost every scratch of his needle. I call it a needle because that describes the fine steel tool which he used. After he had finished the outline he began to work with small, sharp chisels, cutting away the white layer of shell around the figure he had outlined. He worked away carefully, chipping and scraping until it was all removed, leaving the portrait of some old Roman a raised white figure upon a dark ground. It seems simple enough to hear about it, or to see it done, but it requires a skilful hand and a practised eye. There is a finishing process of polishing with putty powder. This is applied with a stiff brush and is said to be a very delicate operation, though it seems as easy as the polishing of a silver spoon." Lucy had been turning over the articles in one of the compartments of the jewel-case and now held up a small cameo pin. "That is a shell cameo!" said Grandma; "I had quite forgotten it. Now if you will observe, you will see that the edges of the raised white part are left square-cut, not rounded or sloped." "Why is that?" asked Lucy. "If the white layer were cut thinner by the rounding or sloping of the edges, the dark layer would show through, and the outline would be less clearly defined." "I see! A very simple explanation." "A great many things are plain after you know the whys and wherefores." "But, grandma," said Lucy, "this set of yours--is this a shell cameo?" "No; I was going to tell you about that. It is very old, and somewhat rare in design and workmanship. It belonged to your great-grandmother Burton. It is an onyx. The art of cutting shell cameos is a modern one. I think it is not a hundred years since shell cameos were introduced, but the art of cutting precious stones like the onyx and agate, in fact, any stone which has layers of different colors, is very ancient. The Greeks and Romans understood the art, and even in Babylonish days it was practised, and used for the ornamenting of vases, cups, urns."