The Absorption of Heat Rays by Fog

Measurements between two stations 0.4 km apart of the intensity of heat rays transmitted through fog showed that, although 7μ rays were slightly less absorbed by fog than visible light, their penetration into fog was too slight to be of practical interest. For a fog of visibility 0.6 km the distances to reduce the light to 10−2 were 910, 970, 980 and 1140 meters for wavelengths 0.6, 1, 3 and 7μ, respectively.