GREENS.—Brilliant greens are produced with great difficulty. We usually take yellow ochre, and after grinding it with spirits, mix it with the powder of Prussian blue, then temper it with a knife, and lay the crayons on the stucco, without rolling them. Instead of this some use King's yellow mixed with Prussian blue, and others brown ochre and Prussian blue. The crayons made of the two last may be rolled. Various tints may be produced by these colours, according to fancy or necessity; some partaking more of the blue, and others of the yellow. Of late many beautiful greens have been invented, such as olympian, emerald, and mineral greens, all which may be used in this art if mixed properly.