U3°3

water for several days; and then dip it repeatedly in thedying liquor, cold, or only lukewarm. The dying liquorconsists of the irony and astringent matters mixed to-gether ; and in the room of, or along with, vitriol, theyuse either filings of iron, or the muddy matter by somecalled flipp, found in the troughs of grindstones whereiron tools are ground. The woollen dyers are sometimesrequired to dye certain pieces of linen black, and in suchcases they practise a method of the same kind; steepingthe piece first in alum water for two or three days, andthen dying it in their mixed black liquor. By this meansthe colour is made to hold somewhat better; but howperishable it still is, we may fee in all black thread.

As the stain produced by solutions of iron is very fixedon linen and cotton; and as the periffiableness of theblack dye seemed to be owing to the astringent matter ofthe galls not sufficiently penetrating or uniting with thevegetable fibre, and therefore too easily coming off, andcarrying the superinduced vitriol with it ; I boiled piecesof linen and cotton, first in solution of vitriol, and after-wards with galls, hoping that the vitriol, fixing itselffirst in the cloth, would make the astringent matter ap-plied upon it likewise fixed. But the event was other-wise! the colour did not prove so black as when thecontrary method of application was followed, and theblackness was rather more destructible.

The colour of indigo and madder being very durableon linen, it was hoped that a ground of these might con-tribute to fix the black. I therefore made trial of sundrypieces of red and blue linen, dying them black by themethods already described. They appeared to have noadvantage above those which had been dyed directly fromwhite: the black was as easily washed out, the blue