Dryers are not mentioned by Cennino, excepting _verderame_ (verdigris,) and that as a mordant. How were the oils made to dry? Will the sun be sufficient? In the summers in Italy their mixed oils readily dry. But in Holland, as in England, for at least a great part of the year, they will not dry of themselves; and it is certain that the longer the pigments are subjected to the action of the oil, the greater is the change. White lead is by no means the best drying colour; and if lead, as a dryer, is so injurious as some will have it to be, to colours in general, why do we not find it so in white lead? Cennino recommends garlic pounded to a juice, and cleared, as a mordant. It is supposed that it gives a drying quality to oil. The practice of the old masters in drying their pictures in the sun--was it only to effect the drying? We believe exposure to the atmosphere is most beneficial to newly painted pictures. We have now a picture before us which was disagreeably oily, and yet did not well bear out. We laid it on the grass, face uppermost, where it lay for about ten days during heat and cold, day and night, dry weather and wet, and in some few burning days exposed to the sun; during these hot days, we had it frequently, plentifully washed with water, left on for the sun to take up. We have this day removed the picture to the easel. The "oily appearance" was gone, it was very dry, but pure, and clean, and bore out equally, but rather like distemper. It is a question worth considering, whether the atmosphere did not take up the impurities of the oil, which always come to the surface.