Transmissivities were measured and absorption coefficients derived for three types of fused quartz between room temperature and 1500 degrees C: GE uv Type 151 (0.21-2.0 mu), GE ir Type 105 (0.21-3.5 mu), and Corning Vycor ir glass No. 7905 (1.7-4.0 mu). Less extensive measurements were also performed with Corning uv Type 7940. The interval of virtual transparency (transmissivity greater, similar0.85) of each type between the ultraviolet and near-infrared was reduced by heating due to a shift in both the long-and short-wavelength absorption edges.