As viridian, like the sea, is naturally "liquid and thin, bright and glassy," the extract we have quoted from Mr. Penley, points to this green as a pigment peculiarly adapted for marine painting; in which, it may be added, its perfect permanence and transparency will be appreciated in glazing. Its fitness for foliage has been remarked; but in draperies the colour will prove equally useful, and in illumination will be found unrivalled. In the last branch of art, indeed, viridian stands alone, not only through its soft rich brilliancy, but by the glowing contrast it presents with other colours: employed as a ground, it throws up the reds, &c., opposed to it, in a marvellous manner. Like the three preceding oxides of chromium, viridian neither injures nor is injured by other pigments; is unaffected by light, damp, or impure air; and is admissible in fresco. In enamelling it cannot be used; the colour, depending on the water of hydration, being destroyed by a strong heat. COPPER GREENS are commercially known as _Emerald Green_, _Malachite Green_, _Scheele's Green_, _Schweinfurt Green_, _Verdigris_, _Green Bice_, _Green Verditer_, _Brunswick Green_, _Vienna Green_, _Hungary Green_, _Green Lake_, _Mineral Green_, _Patent Green_, _Mountain Green_, _Marine Green_, _Saxon Green_, _French Green_, _African Green_, _Persian Green_, _Swedish Green_, _Olympian Green_, _Imperial Green_, _Mitis Green_, _Pickle Green_, &c. The general characteristics of these greens are brightness of colour, well suited to the purposes of house-painting, but seldom adapted to the modesty of nature in fine art; considerable permanence, except when exposed to the action of damp and impure air, which ultimately blacken most of them; and good body. They have a tendency to darken by time, dry well as a rule in oil, and are all more or less poisonous, even those not containing arsenic. 179. EMERALD GREEN,