An International Correspondence Schools instruction paper (Serial 471) on drying scoured wool in woolen mills. It explains why high temperatures harm the fiber, then describes cold-air table dryers, multiple-apron hot-air dryers, and two-compartment sectional dryers, with operating temperatures, construction details and a capacity table. The last part covers hydro-extractors, both the self-balancing type and the Weston gyrating-basket type, with line drawings of each machine.