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From the watery infusion of wood soot is prepared thebrown pigment called bistre, for painting in water colours..According to Mr. Landois, in the French encyclopedie, thefoot is either boiled in water, or ground with a little urine(water will do as well) into a smooth paste, and thendiluted with more water : after standing for about half anhour, till the grosser substance of the foot has settled, theliquor is poured off into another vessel, and set by for twoor three days, that the finer parts may fall to the bottom,which fine matter is the bistre. That the bistre of ourcolour strops has been prepared by a process of this kind,and not, as some have suspected, by evaporating the infu-sion of soot to an extract, may be presumed both from itsappearance and its qualities. It is in little masses, such asare obtained in the common way of drying precipitates,or earthy powders that have been ground with water, bydropping them on a chalk stone. It readily mingles withwater, and continues fora time uniformly diffused throughthe fluid : a considerable part was observed to settle in anhour or two, a part more flowly, and after standing formany weeks a part remained dissolved in the water, so asto tinge it of a browniih-yellow colour, like a weak in-fusion of foot: this tinged liquor passed through a filter,without any separation of the colouring matter. In thepreparation of the bistre, when the soot liquor has deposit-ed all that will fettle, the sediment, however drained, willnecessarily retain some of the coloured fluid, which, dry-ing, will leave in it some of the truly dissoluble parts ofthe foot; and hence probably proceeds the matter in bistrewhich we find to continue dissolved in water, the propor-tion of which is inconsiderable, compared to that whichprecipitates. .Different parcels of bistre differ consider-ably in their colouff on account, probably, of the differentqualities of the foots which they were made from.

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