Wood is preserved by any agents which destroy the tendency to putrefaction of the matter within its pores, or which enables it to resist the attacks of insects, or renders it unsuited to the growth of minute fungi. See Dry-rot.
WOOD NAPH′THA. See Spirit (Pyroxylic).
WOOD OIL. See Balsam, Gurgun.
WOODY FIBRE. See Lignin.
WOODY NIGHT′SHADE Bitter-sweet, Solanum dulcamara.
WOOL. Syn. Lana, L. Wool is a fine, soft, elastic variety of hair, cellulated in its structure. Its filaments are cylindrical, like those of silk; but the surface is covered with thin scales or epidermic cells. In the finer qualities, these filaments vary in thickness from 1⁄1100 to 1⁄1500 of an inch; and under a good microscope distinctly exhibit, at intervals of about 1⁄300 of an inch, a series of serrated rings, imbricated towards each other, “like the joints of equisetum, or, rather, like the scaly zones of a serpent’s skin.” These appearances render it almost impossible to mistake wool for silk, linen, or cotton. From experiments made by different competent authorities, it is found that wool is one of the worst conductors of heat known. This property renders woollen fabrics particularly adapted for clothing in cold, damp, and changeable climates, since it enables them to maintain the surface of the body at a proper and equable temperature. Wool, sometimes, however, proves too irritative for highly sensitive skins, and, moreover, disturbs the electricity of the cutaneous surface, on friction, even more than silk. On these accounts there are persons who find it unpleasant to wear woollen garments, of any description, next the skin; in which cases all the advantages that can be derived from their use may be
obtained by wearing them outside one of linen or cotton. According to Erasmus Wilson, this method “is preferable in warm weather, since the linen absorbs the perspiration, while the woollen garment preserves the warmth of the body, and prevents the inconvenience resulting from its evaporation.” See Flannel.
Identif. 1. By the microscope. (See above.)
2. Its fibres, when inflamed, shrivel up, and burn with difficulty, and evolve the peculiar and characteristic odour of hair when similarly treated, leaving a bulky charcoal; whereas cotton and linen burn rapidly, leave no charcoal, and evolve little or no odour. Silk acts in nearly the same manner as wool.
3. Nitric acid, picric acid, and gaseous chlorine, stain the fibres of wool and silk yellow. Dr J. J. Pohl recommends an aqueous or alcoholic solution of picric acid as well adapted for a test—After immersion of a small portion of the fabric or yarn for from 5 to 10 minutes in the solution, it is to be taken out, and washed in warm water. The linen and cotton in it will then appear white, but the wool, silk, or other animal fibre, will retain its yellow colour. In stuffs, cloths, flannel, &c., the mixed threads may be readily observed by means of a pocket lens, and their relative numbers may be ascertained by means of a ‘thread counter.’ This test acts best with white, but is also applicable to many other colours. For dark colours nitric acid is preferable.