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50 was dry, but a little sticky, & yellow at the edges; the Magnesia was perfectly clear & dry; the Carbonate of Zinc, not at all dried, but unchanged; the calcined Sulphate of Zinc, not dry; and the Alumine not dry. White mixed with the Acetate of Lead, dry, a little sticky & yellowish; [[strikethrough]] then [[/strikethrough]] with the Magnesia perfectly white & dry; with the others not dry. This experimental comparison shows a decided preference for Magnesia instead of [[strikethrough]] Magnesia [[/strikethrough]] Alumine, or the Carbonate or Calcined Sulphate of Zinc; although the last article is so often recommended as the best in Theoretical Treatises on the Art. At the same time, & for weeks afterwards, the Counterparts of the mixtures [[strikethrough]] of tints [[/strikethrough]] exposed to the Sun, both by themselves, & combined with various tints of Colours, showed that the Magnesia alone remained perfectly clear; whilst all the others, although dry, were already embrowned; and in a few weeks the Calcined Sulphate of Zinc had become of an Opake White, with but little cohesion; and mixed with White, was somewhat yellowish. My conclusion, therefore is, that Calcined Sulphate of Zinc is unfit for a drier, & cannot supercede the Acetate of Lead, or good drying oil - and a long Course of practice confirms the merits of Magnesia as the most brilliant diluent. Sandarac in Oil. It appears from the learned Researchers of Mr. Eastlake ‡ that it was the practice of the early Flemish and Italian Artists, who were the most eminent for their colouring & facility of execution, to employ oils that held Resins in solution. I have repeated some of the Recipes recorded, and find some advantage in their use. Gum Mastic may be dissolved in Poppy or Linseed oil, by long continuance in the heat of a sand or Water bath. The oil thus prepared is lighter coloured & but little thickened, & seems to dry more slowly, and with a lustre, not sinking in, but has not much solidity. Rosin dissolves more readily, makes the oil lighter coloured & gives lustre to the Colours. Gum Sandarac, reduced to a powder and long digested in a sand bath with considerable heat, with good drying oil of Linseed, in part dissolves, rendering the oil of a reddish hue. It dries well and possesses the advantage of giving † In his "Materials for a history of Oil painting,