Cotton cambric piece-goods are passed through a blotching machine to receive a mordant of acetate of iron, and galled slightly; sumach is used instead when galls are dear; the cotton is then passed through logwood, or logwood and fustic, and then through sumach; so that it is possible thus to give them the mordant sufficiently in proportion to the iron liquor at first; proceed as in dyeing afterwards, at a heat approaching boiling or even boiling. You may now proceed by adding first the galling or sumach slightly; afterwards the logwood, &c.; and then the remainder of the galling or sumach may be used to finish it; and thus dye the goods black by the quickest possible process. It should be observed respecting the last process and the process which precedes it, that in dyeing black alum is inimical to the colour. Therefore D'Apligny's is not now esteemed. Alum for black is as improper, as it is proper and essential for red and yellow. In regard to giving the acetate of iron for black at once, as the second, or _London_ process directs, it may be done by having the proportions full; by _full_ is meant that the mordant should be full enough; then, after the slight galling, as directed in giving the logwood and alder bark decoction, or logwood and fustic, be sure to have that decoction strong enough. This might be called the ground; and the most perfect judgment might be formed of it by having a part of a piece, or one piece of a batch dried in the stove: for, according to the fullness of the ground, so will the black be rich and perfect or otherwise. The alder bark and fustic are used only to prevent the hue of the logwood from being predominant. If the ground be a full and rich brown, the second full galling or sumaching will bring it to a full and rich black; but, if the ground be poor, these processes will cut or destroy the ground, and the black will be foxy, nasty, and poor; and not only so, but the material dyed will soon wear rotten, because having an over-dose of iron, the iron will tend to decompose the cotton. Therefore the following process is most esteemed. _For dyeing_ BLACK _(particularly cotton velvets) at Manchester._ In a large dye-house where much business is done, a great many wine-pipes or other large tubs, or any substitutes are arranged in an appropriate place. Into these are put old iron hoops, rusted in the air, and cut into short pieces; a layer of the iron pieces and a layer of the alder bark, again a layer of iron and a layer of the bark, and so on in succession from the bottom to the top. When the pipes are all thus filled, water is poured into them till they are filled up; they remain in this state for six weeks or two months according to the season, whether summer or winter. The same process will do for any other cotton goods as well as velvets, such as calicoes, cambric, and jaconot muslins, cotton in the skein, &c.