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An astringent matter might be introduced aiio into 1parchment and vellum. The common tanned skins, asalready observed, and not only those of the softer kindbut the firm soles of slioes, have the very impregnation,which we here propose to communicate to the finer skinsused for writing. I steeped a thick piece of parchmentin water, along with some oak bark, for three or fourdays, and having then pressed it smooth and dried it, Ifound it as effectually penetrated with the matter whichmakes ink durable, as the paper in the experiment beforementioned. Even when the surface of the parchmentwas pared off', and the internal part written upon, thecharacters continued of a good black, while those madewith the fame ink, on unprepared parchment, werechanged to a yellowish brown.

It may here be observed, that an impregnation ofpaper with one or both of the ingredients of ink, hasbeen sometimes already practised, in a more imperfectmanner, and with a view rather to amusement, than tothe answering of any useful purpose. Galls in fine powderbeing well rubbed into the paper with a hares foot, asolution of vitriol, made so dilute as to have little or nocolour, writes black upon the paper so prepared, formingwith the galls, in all the parts it touches, an extempo-raneous ink upon the surface of the paper. If powderedvitriol be first rubbed in, the same blackness is producedby infusion of galls ; and if powdered galls and powderedvitriol be mixed and applied together, both in a very drystate that they may not act upon one another, plain watermakes a black writing.

But though practices of this kind should in some cafesbe convenient; as for making occasional minutes, in wantof ink, with common watery fluids; or for the purposementioned by Boyle, the keeping of the singers from being

F f f blacked,