Crayons or pastils consist of various coloured pigments or paints, formed into sticks or rolls for the purpose of drawing and shading with them in the manner of lead pencils. But that they may be of uniform texture or hardness, different ingredients and materials require some variation in the management. To make white crayons, nothing more is requisite than to mix superfine or refined whiting with alcohol, to the consistence of soft putty; form it into rolls of a convenient length and size and let them dry: or the whiting may be mixed with water and a sufficient quantity of burnt or calcined sulphate of lime to give the crayons a sufficient degree of hardness when dry. A great variety of elegant light colours may be formed by adding to the whiting prepared as above, small quantities of any of the coloured pigments. The most proper colors for crayons are lamp-black, prussian blue, burnt umber, burnt terra-de-sienna, red ochre, vermilion, lake, rose-pink, chrome yellow, yellow ochre and mineral green. Many other handsome greens are formed by mixing chrome yellow with prussian blue, varying the proportions; and purples are produced by mixing rose pink or lake with blue. Prussian blue and lake being each naturally of a binding nature, require only to be ground in water; but red ochre and vermilion should be ground in alcohol, or may have some quantity of the sulphate of lime mixed with them. Any of these colours may be mixed in any proportion with whiting or with each other, each compound having a sufficient proportion of the sulphate of lime, to give it a proper degree of hardness and strength when dry. The proper length for crayons is from two to three inches, and the size about the same as that of a tobacco-pipe stem. It is customary in making crayons, to have at hand a large piece of chalk with a plane surface, on which to lay the crayons as soon as they are rolled; the chalk absorbs a part of the moisture, which makes them dry the sooner and without cracking.