But not with the red of the ruby, the blue of the gentian, snow for the light, and amber for the gold, could such a picture be produced, if the masses of those colours were kept unbroken in purity, and unvarying in depth. Olive being usually a compound colour both with the artist and mechanic, there are few olive pigments in commerce. 232. MIXED OLIVE may be compounded in several ways; directly, by mixing green and purple; or indirectly, by adding to blue a smaller proportion of yellow and red, or by breaking much blue with little orange. Cool black pigments, combined with yellow ochre, afford eligible olives; hues which are called _green_ in landscape, and _invisible green_ in mechanic painting. It is to be noted that in producing these and other compound colours on the palette or canvass, those mixtures will most conduce to the harmony of the performance which are formed of pigments otherwise generally employed in the picture. Thus, presuming aureolin to be the principal yellow used, the same yellow should be chosen for compounding orange and green, or for obtaining indirectly citrine, russet, and olive. PERMANENT GREEN. | PERMANENT PURPLE. | Oxide of Chromium, opaque. | Mars Violet, true. Oxide of Chromium, transparent. | Purple Madder. Veronese Green. | Viridian. | Emerald Green. | Scheele's Green. | Terre Verte. | As in the case of russet, there may be added to the two original purples, mixtures composed of durable reds and blues. There are so many ways of producing the tertiaries, that no difficulty can be found in compounding them with stable pigments. Each tertiary may be represented as follows:-- CITRINE = Orange + Green. " = (Yellow + Red) + (Yellow + Blue.) " = 2 Yellow + Red + Blue. RUSSET = Orange + Purple. " = (Yellow + Red) + (Red + Blue.) " = 2 Red + Yellow + Blue. OLIVE = Green + Purple. " = (Yellow + Blue) + (Red + Blue.) " = 2 Blue + Yellow + Red. From the above equations, and by consulting the lists given of permanent primary and secondary colours, the artist will at once see how easily and safely he may vary his mode of compounding the tertiaries. 233. OLIVE GREEN,