Lead may be readily worked with rasps, but it clogs files so much as to render it difficult to produce a smooth surface by those instruments; in practice it is generally scraped for the smoothest surfaces. Lead is not often polished, it would require to be treated like pewter but with greater care, to prevent the formation of utters in the scraping or burnishing.
LENSES. - See Chap. XXXIII. Section 4.
LIME is occasionally used as a polishing material on account of its cheapness, as the only preparation required is to slake the lime with a little water, it then falls to a fine powder and which is sometimes sifted. Lime is used for polishing the commonest works in bone, such as brushes, and also for Albata Spoons.
LIMESTONES. - The substances to which this name is applied differ greatly in hardness and compactness. Some are so soft as not to admit of being polished, and are treated much the same as the Freestones, (which see,) whereas, those limestones which do admit of being polished, are generally designated under the name marble, the mode of polishing which is minutely described under that head.
LOAM is used with water by some manufacturers as a cheap material with which to grind in the conical plugs of brass valves and cocks. Loam contains more silex than the generality of the clays, but which also are occasionally used for polishing common works.
MALACHITE, or the massive green carbonate of copper, is much used for jewellery and articles of vertu, the finest malachite is from Russia, and as it is traversed by numerous circular fissures; from the imperfect joinings of the botryoidal masses of which it may be considered to be composed; it is difficult to polish, and requires great care and attention; notwithstanding its hardness it is considered by some lapidaries better to treat it as alabaster than carnelian, but each method is followed.
MEERSCHAUM is scraped to a smooth surface, but it is so soft as scarcely to admit of being polished, otherwise than by dipping the meerschaum into melted wax to fill up its pores, and rubbing it when dry with a flannel; and which is the usual process. Milk Meerschaum obtains a somewhat different treatment.
MOSLINGS. - The thin shreds or shavings of leather shaved off by the currier in dressing cow, or calf skins. They are frequently used for removing oil from metals that are being polished and serve extremely well, being as bibulous as blotting paper. Cotton waste is similarly employed especially in the vicinity of cotton mills.