This useful, but, when used too freely, mischievious preparation, is for sale at all colorshops at a very moderate price. It is made by boiling gently, in linseed-oil, litharge, ceruse, umber, and powdered talc; of each half an ounce, to a pound of the oil. Such being its ordinary composition, though there are other modes of preparing it, we need not look at its dark brown color, nor breathe its nauseous odor, to be deterred from using it, except where necessary.,,It loses some of its color by age; and is not always obtained of uniform quality. We have had some from the colorman's which in a very few weeks deposited a considerable sediment, and became as light as simple boiled oil. The probability is that it had been imperfectly prepared, and that, the sediment thus deposited, it was nothing more than simple boiled oil. We have a portion of it left, which we poured from the dregs, and which has become useless by hardening. It presents exactly the appearance of boiled linseed-oil that, by standing a very long time in the bottle, has bleached at once and stiffened. Two other samples that we got of the same manufacturer a little more than a twelvemonth ago, have deposited a small quantity of sediment that just covers the bottom of the phials; and, held up to the light, they sjow that the precipitation is continuing. It is evident therefore, that, as Watin says, "the older it is, the better,"- provided it be not too thick.,