UV rays cause organic and inorganic substances to phosphoresce. In contrast fluorescent substances which cease to glow immediately after the exciting rays are shut off, phosphorescent substances continue to emit visible light after the exciting radiations have ceased. Contains charts of the following tests: Effect of light exposure on phosphorescence and fluorescence of undyed fabrics; Comparative phosphorescence of undyed textile fabrics; Phosphorescence and fluorescence of undyed and dyed fabrics; Phosphorescence and fluorescence of undyed yarns; Phosphorescence and fluorescence of undyed paper; Phosphorescence and fluorescence of human hair; Phosphorescence and fluorescence of carao, istle, jute, and sisal, and Phosphorescence and fluorescence of miscellaneous compounds.