Wool's composition in the raw state is threefold. Thus there is the wool-yolk - what may be termed a natural impurity; the wool fat, which is not only present in the yolk but also permeates the fibre and seems to give it its plastic and soft handle; and the cell structure proper of the fibre. Fleece wool comes into the market unwashed with all the dirt which gathers to the surface of the greasy wool; or it is received as "washed" wool, the wool washing being done as a preliminary to the sheep-shearing, or in some cases, it is scoured and is consequently stated as "scoured". Where there is abundance of water and other conveniences it is the practice to do wool washing or half-washing of sheep previous to shearing, and such wool comes into market as washed or half washed- fleece. The surface of a fleece has usually a thick coating of dirt, and in the case of merino breeds the fleece surface is firmly caked together into solid masses, so that in fleece without wool washing 30% of weight may represent dirt, and about 40% the greasy suint which lubricates the wool, while the pure wool is not more than one third part of the whole. Sheep washing appliences are employed, the arrangement consisting of a pen into which the sheep are driven and subjected to a strong spray of water either hot or cold, which soaks the fleece and softens the dirt. This done, they are caused to swim along a tank which narrows towards the exit, and just as they pass out of pen they are caught and subjected to a strong douche of pure water. They should then be kept on grass land free from straw, sand etc., so that the wool may be sheared free from vegetable matter, etc. After wool wasing, the wool of a washed sheep is sufficiently dry for shearing or clipping. The wool washing which a fleece may have received on the live sheep is not sufficient to avoid color bleeding in fabrics manufacturing. Much depend on careful scouring. The quality of the fiber may be seriously injured by treatment, while, if the wool is imperfectly cleansed, it will dye unevenly, decoloration may happen, and the manufacturing operations will be unsatisfactory. The water used for scouring should be soft and pure, both to save soap and because the insoluble lime soap formed in dissolving soap in hard water is deposited on the wool fibers and becomes so fixed that its removal is a matter of extreme difficulty. Wool washing machines ensure the passage of the wool without lifting and "stringing", to obviate the mixing of wool grease, sand, dirt, etc., once taken out of the wool with that wool again, to give time for the action of scouring agents, so that neither too strong a solution nor too great a heat be employed. Worsted yarn manufacture is done with the help of "water frame". In order to obtain a sliver, which can be satisfactorily spun into a typical worsted thread five or six operations are necessary and one of them is back-wasing. The slivers during their passage through the preparing-boxes become sullied naturally, and in addition, owing to the opening out of the locks of wool, dirt which was not "got at" in the scouring now works out and further sullies the slivers. It is consequently necessary to do wool washing again, this being effected in what is termed a back-washing machine. The machine usually consists of two scouring tanks with immersing rollers, drying cylinders, a gill-box and oiling motion. To sum it up, those are wool washing methods that allow avoiding fabrics' color bleeding and discoloration.