An International Correspondence Schools instruction paper on wool as a textile fiber. It covers the classification of textile fibers, the structure and growth of the wool fiber, and wool's properties (felting, fineness, strength, crimp, luster, hygroscopicity). It then treats wool substitutes (shoddy, mungo, extract), sheep breeds and world wool supply, mohair, and wool sorting by fleece region. It ends with wool-sorters' disease and a glossary of trade terms. Illustrated with micrographs of fibers and diagrams of fleece quality zones.