The foregoing yellows and blues are in no wise inimical to each other, and yield the best mixed greens, chemically considered, the palette can afford. In an artistic sense, we confess, the result is not so satisfactory: the list of blues, it must be admitted, being somewhat scant. Among the latter there is no pigment with the wonderful depth, richness, and transparency of Prussian blue, and none consequently which will furnish with yellow a green of similar quality. That the artist, therefore, will dispense with Prussian blue, it would be too much to expect. There is, however, less necessity for it since the introduction of viridian, a green resembling that which is produced by admixture of Prussian blue and yellow, and which may be varied in hue by being compounded with aureolin or ultramarine. Our object in this work is to give precedence to the chemical rather than the artistic properties of pigments, to separate the strictly stable from the semi-stable, and the semi-stable from the fugitive. A colour or a mixture may be chemically bad but artistically good, and vice versâ; but the chemist looks upon no pigment or compound with favour unless it be perfectly permanent, and ignores its mere beauty when void of durability. Hence, all artistic considerations are set aside in our lists of permanent pigments: if it be possible to use them alone, so much the better for the permanence of painting; if not, so much the worse will it be, according to the degree of fugacity of the colours employed. 184. BRONZE, and the three succeeding varieties, are greens resembling each other in being semi-stable, and more or less transparent. Bronze is a species of Prussian green, of a dull blue-black hue. In its deep washes it appears a greenish-black with a coppery cast. It is used in ornamental work, and sometimes as a background tint for flower pieces. 185. CHROME GREENS, commonly so called, are compounds of chromate of lead and Prussian blue, a mixture which is also known as _Brunswick Green_. Fine bright greens, they are suited to the ordinary purposes of mechanic painting, but are quite unfit for the artist's craft, chrome yellow reacting upon and ultimately destroying Prussian blue when mixed therewith. For the latter, cheap cobalts and ultramarines are preferably substituted, although they do not yield greens of like power and intensity.