Installment of E. A. Posselt's serial "Fabric Analysis" (December 1911), section IV on ascertaining the raw materials in yarns and fabrics. It contrasts physical and chemical tests, describes the compound microscope and how to prepare yarns and fibres for it, and explains the microscopic appearance of wool fibres, woolen versus worsted slivers, and imperfect fibres (untrue fibres and kemps), illustrated with figures. The pages also include a short passage describing a jacquard doup-heddle for leno and a brief note on Irish cotton spinning.