A 1931 paper by E. R. Schwarz of M. I. T. surveying new developments in textile microscopy, presented to ASTM Committee D-13 in October 1930. It covers specialized microscopes and mounting and measuring equipment, a quick low-cost method for cutting fiber cross sections (the Schwarz slide), Rheinberg colored dark-field illumination, and polarized light. It also discusses the handling and statistical treatment of data, applied mill research with pocket and stereoscopic microscopes, and prospects for x-ray, fluorescence, and photoelectric methods. Illustrated with seven photomicrographs and apparatus figures.