CHARACTERISTICS AND PROPERTIES OE WOOL. W001 is a living appendage of the skin. produced by increased epidermal cells. 'the difference be t wool wool and hair is one of degree rather than of kind, because all wool bearing animals have the tendency when licUleet cd to produce hair rather than wool, and because numerous inter mediate structural stages exist between the two extremes. While wool is eommonly character ized by its line, soft, curly nature, the true distinction bet ween it and hair lies in its cover ing of pointed scales or plates, attached to the filament at their bases and overlapping much like fish-scales. This structure, which is readily seen with a microscope, is perceptible to the touch by its harsh. rough feeling when the fibre is drawn through the fingers from the tip to the root. The number of these scales hears a fairly direct relation to fineness of the fibre. The curli ness of wool is due to it spiral structure of the filaments, and although all wool is not curly or curliness is one of ifs recognized and im portant characteristics. There also appears to be a relation between fineness and curliness. Owing to the relation which these three charac teristics hear to each other, curliness, or the number of waves to the inch, which can in' seen With the naked eye, is one of the factors noted in judging of wool. The waviness and scaliness are utilized in making felt (q.v.) and also in thread-making. A pound of the ti nest wool will yield nearly 100 miles of thread. ln spin ning, the filaments interlock by their scales. and the curl of the fibre prevents the threads and helps to hold them together. These valuable qualities vary greatly in dif ferent wools. some being adapted to carding for cloth, and others to combing for It is upon minute points of difference that the value of various grades of wool chiefly depends. The lustre also differs greatly and to a certain extent is a breed characteristic, the wool of the Lincoln and the best Leicester sheep being much more lustrous than that of the shorter wools or the fine :Merino fleece. The length of staple,
which is made a basis of general classification, is largely a constitutional or breed characteristic, the staple being from one to two inches long in the finest :Merinos, eight inches or more in the Lineolns, and reaching twelve and even fifteen inches in some combing wools. the length of staple suggesting the grouping of sheep into short-wools. middle-wools, and The fine felting wools have a short staple. as a rule, and are used for carding or yarn purposes. while the longer, more lustrous. and less wavy ones are Letter suited to combing and worsteds.
Another valuable characteristic of wool is its elasticity, whieh gives it a softness to the touch which is retained in the manufactured goods. Closely related to this is the strength of fibre; a dead or inferior wool will break instead of stretching when strained. Delicate machines have been constructed for testing the strength and elasticity of fibre, for both practical and scientific purposes. Rowman found that wool fibre is fully one-fourth stronger than cotton. the strength being proportional to the diameter. Great variation, however, exists in the strength of fibres front different wools of the same class of sheep.
All wool in its natural state contains fatty or greasy matter called yolk or saint, secreted by the skin and covering the individual hairs. This serves to lubricate the fibres and prevent their matting together, and also protects the fleece from injury. It differs in quantity and exact elmracter with various breeds and is believed to render the wool soft and pliable. The fats and the potash salts which the yolk contains form a sort of natural soap. For manufacturing pur poses the yolk. which tc partly soluble in water, must be removed so as to increase the felting tendency and the ability of the wool to take dye.
White is the most common color of cleaned wool, and is generally preferred for manufactur ing; 'nit the black, fawn, cream, and gray shades produced by various breeds are utilized in their natural colors for certain kinds of clothing.