The effective scattering and absorption cross sections were determined from measurements of radiant transmission through isothermal beds of glass, aluminum oxide, steel and silicon carbide spheres, cylinders, and irregular grains. The radiant conductivities were calculated from these cross sections. Back scattering was found to be the principal mechanism of attenuation for all of the packings. Absorption was a significant mechanism only for the silicon carbide grains. At 2,000°F. The radiant contribution to the total heat flux was estimated to vary from 35% for the silicon carbide packings to 85% for the glass packings.