is obtained from the stone after the richer and more intense blue has been extracted. Although not equal in beauty, and inferior in strength of colour to ultramarine, it is a valuable bye-product varying in shade from light to dark, and in hue from pale azure to cold blue. With a grey cast, it affords delicate and extremely tender tints, not so positive as ultramarine, but which, as water-colours, wash much better. It furnishes grays softer, purer, and more suited to the pearly tints of flesh, skies, distances, foliage, shadows of drapery, &c. than those composed of other blues, with white and black, which the old masters were wont to employ. Ultramarine, however, produces the same effects when broken with black and white, and is thus sometimes carried throughout the colouring of a picture. The ash, compounded with lamp black, gives a soft cold gray for dark louring clouds, or for twilight away from the sun's influence. Alone it is adapted to very remote hills or mountains, and with orient yellow or aureolin to distant foliage. * * * * * The native phosphate of iron, which has been already described in the tenth chapter under its name of Blue Ochre, might have been classed among the grays, being similar in colour to the deeper hues of ultramarine ashes. Powdered slate, slate clays, and several native earths, likewise rank with grays; but some of the earths we have tried are not durable, being apt to become brown by the oxidation of the iron they contain. It may be proper here to mention those other pigments, known as tints, which, being the result of the experience of accredited masters in their peculiar modes of practice, serve to facilitate the progress of their amateur pupils, while they are more or less eligible for artists. Such are _Harding's_ and _Macpherson's Tints_, composed of pigments which associate cordially, and sold ready prepared in cakes and boxes for miniature and water painting. Of the four grays in use--mineral gray, ultramarine ash, neutral tint, and Payne's gray--the two first are quite unchangeable, and the others sufficiently stable to be classed as permanent. CHAPTER XX. ON THE NEUTRAL, GREY.