White Chalk is a well-known native carbonate of lime, used by the artist only as a crayon, or for tracing his designs; for which purpose it is sawed into lengths suited to the portcrayon. White crayons and tracing-chalks, to be good, must work and cut free from grit. From this material whitening and lime are prepared, and are the bases of many common pigments and colours used in distemper, paper-staining, etc.

There are many other terrene whites under equivocal names, from the famed Meliiintn, or white earth of Melos, mentioned by Pliny to have been used by the Greek painters, to common whitening prepared from chalk. Among them are Moral or Modan while, Spanish white, or Troys, or Troy white, Rouen white, Bongeral white, Paris white, Blanc de Roi, China white, Satin while, the latter of which is a sulphate of lime and illumine which dries with a glossy surface, etc. The common oyster-shell contains also a soft white in its thick part, which is good in water; and egg-shells have been prepared for the same purpose; as may likewise an endless variety of native earths, as well as those produced by art. From this unlimited variety of terrene whites we have selected above such only as are reputed, or as principally merit the attention of the artist; - the rest may be variously useful to the paper-stainer, plasterer, and painter in distemper; but the whole of them are destitute of body in oil, and, owing to their alkaline nature, are injurious to many colours in water, as they are to all colours which cannot be employed in fresco. See Table 9, Chap. xxii.