native or artificial, are well represented on the palette, but nothing would be easier than to increase their number. Of all metals, iron is the richest source of colour, capable of affording all colours with the exception of white. None of them, however, are so numerous as the browns, a description of which would fill this chapter. Suffice it to state they are obtainable of every hue, tint, and shade, and are generally permanent. They are made on a large scale and sold under various names for house-painting, &c. 269. _Manganese Brown_ is an oxide of manganese, which is quite durable both in water and oil, and dries admirably in the latter. A fine, deep, semi-opaque brown of good body, it is deficient in transparency, but might be useful for glazing or lowering the tone of white without tinging it, and as a local colour in draperies, &c. 270. _Nickel Brown._ A very pleasing yellowish brown is obtainable from nickel, bright and clear in its pale washes, and of some richness in oil. Unless thoroughly washed, it has a tendency to greenness in time. 271. _Ochre Browns._ The slight affinity of sulphur for yellow ochre, with its merely temporary effect thereon, was observed in the eighth chapter, where allusion was made to the action of sulphuretted hydrogen and sulphide of ammonium on the earth. Sulphur alone, and in the dry state, ignited with yellow or other native ochres converts them into browns, varying in hue, and of greater or less durability. Those browns, however, which we have made by this process, although standing well in a book, have not withstood exposure to light and air. They have all become pale, whitish, or of a drab cast, evidently through the oxidation of the sulphur, or rather the sulphide of iron formed during the calcination. Practically, therefore, ochres have an antipathy to sulphur, moist or dry, by itself or in combination; and are, so to speak, the disinfectants of the palette. Ever waging war against sulphurous vapours, the native earths serve to protect a picture from the damaging influence of impure air, whether they be used alone, or employed in admixture with such pigments as are injured thereby. 272. _Purple Brown_ is a refuse manufacture from Indian red washings. A dull, heavy, coarse colour, it belongs to the class of common pigments which are unexceptionable for decorative painting, but scarcely suited to the higher branches of art. As this work professes simply to treat of artistic pigments, that have been, are, or might be, more than a passing reference to those colours exclusively adopted by house-painters, &c., would be out of place. 273. _Rubens' Brown_, still in use in the Netherlands under this appellation, is an earth of a lighter colour and more ochrous texture than the Vandyke brown of English commerce: it is also of a warmer or more tawny hue than the latter pigment. Beautiful and durable, it works well both in water and oil, and much resembles the brown employed by Teniers.