Ivory and bone admit of being turned very smooth, or when filed may afterwards be scraped so as to present a good surface. They may be polished by rubbing first with fine glass-paper, and then with a piece of wet linen cloth dipped in powdered pumice. This will give a very fine surface, and the final polish may be produced by washed chalk or fine whiting applied by a piece of cloth wetted with soapsuds. Care must be taken in this, and in every instance where articles of different fineness are used, that, previous to applying a finer, every particle of the coarser material is removed, and that the rags are clean and free from grit. Ornamental work must be polished with the same materials as plain work, using brushes instead of linen, and rubbing as little as possible, otherwise the more prominent parts will be injured. The polishing material should be washed off with clean water, and when dry, may be rubbed with a clean brush.

Horn and tortoiseshell are so similar in their nature and texture that they may be classed together. As regards the general mode of working and polishing them, a very perfect surface is given by scraping. The scraper may be made of a razor-blade, the edge of which should be rubbed upon an oilstone, holding the blade nearly upright, so as to form an edge like that of a currier's knife, which may be sharpened by burnishing. Work when properly scraped is prepared for polishing. To effect this it is first rubbed with a buff made of woollen cloth perfectly free from grease. The cloth may be fixed upon a stick to be used by hand; but a "bob," which is a wheel running in the lathe and covered with the cloth, is much to be preferred on account of the rapidity of motion. The buff may be covered either with powdered charcoal and water, or fine brick-dust and water. After the work has been made as smooth as possible with this, it is followed by another bob on which washed chalk or dry whiting is rubbed. - The article to be polished is slightly moistened with vinegar, and the buff and whiting will' produce a fine gloss, which may be completed by rubbing with the palm of the hand and a small portion of dry whiting or rotten-stone.

(a) Well scrape with glass or steel scraper, afterwards with finest glass-cloth, then with powdered bath brick and oil, and finally with rotten-stone and flannel, or old cloth or felt hat.

(6) First scrape with glass to take off any roughness, then grind some pumice to powder, and with a piece of cloth wetted and dipped in the powder, rub them until a smooth face is obtained. Next polish with rotten-stone and linseed oil, and finish with dry flour and a piece of clean linen rag. The more rubbing with the stone and oil, the better the polish. Trent sand is used in the Sheffield factories. It is a very fine and sharp sand, and is prepared for use by calcining and sifting.