By numerous methods both wet and dry, oxides of chromium are obtainable pale and deep, bright and subdued, warm and cool, opaque and transparent: sometimes hydrated, in which case they cannot be employed in enamelling; and sometimes anhydrous, when they are admissible therein. But whatever their properties may be, chemical, physical, or artistic, they are all strictly stable. Neither giving nor receiving injury by admixture, equally unaffected by foul gas and exposure to light, air, or damp, these oxides are perfectly unexceptionable in every respect. For the most part they are eligible in water and oil, drying well in the latter vehicle, and requiring in the former much gum. They have long been known as affording pure, natural, and durable tints; but, until within the last few years, have been rather fine than brilliant greens. Lately, however, processes have been devised, yielding them almost as bright, rich, and transparent, as the carmine of cochineal itself. 175. OXIDE OF CHROMIUM, _Opaque Oxide of Chromium_, _Green Oxide of Chromium_, _Chrome Oxide_, _True Chrome Green_, _Native Green_, _&c._, is found native in an impure state as Chrome Ochre, but is always artificially prepared for artistic use. Obtained anhydrous by dry modes, this is the only chrome oxide available in enamelling, and is the one seen on superior porcelain. It is a cold, sober sage green, deep-toned, opaque, and, although dull, agreeable to the eye. Its tints with white are peculiarly delicate and pleasing, possessing a silvery luminous quality, and giving the effect of atmosphere. Being very dense and powerful, it must be employed with care to avoid heaviness, and is preferably diluted with a large quantity of white, or compounded with transparent yellow. In the hands of a master, this gray-green furnishes lustrous hues with brown pink, Italian pink, and Indian yellow; three beautiful but fugitive pigments, of which the two last may be replaced by aureolin. Of this Mr. Penley observes, "as adapted for the colouring of foliage and herbage, it is impossible to say too much in its praise. It imparts the vividness and freshness of nature to every colour with which it is combined;" and he brackets oxide of chromium with aureolin as a compound hue "extremely useful." In flat tints, the oxide sometimes does not wash well in water. 176. TRANSPARENT OXIDE OF CHROMIUM being deficient in body, is only eligible in oil. A very pale greyish-white green in powder, it gives an agreeable yellowish green of some depth in oil, moderately bright, but not very pure or clear. We are acquainted with another transparent chrome oxide of far greater beauty, brightness, purity, and clearness than the above. Of a bluish green hue, a difficulty in getting it to mix with oil renders it at present unavailable. 177. VERONESE GREEN,