The absorption coefficient of chemically pure, fairly dust free water was measured by photographic photometry by using tubes of water up to 272 cm long. γ, defined by i=i0e−γx, where x is in cm, was 0.8, 1.9, 4.3, 7.7, 13.5 and 80×10−3 at wave-lengths 4000, 3600, 3200, 2800, 2400 and 2000A, respectively. The values were more than 10 times those calculated from molecular scattering. For the visible wave-lengths 5400, 5890, 6700 and 6900A γ was 0.0004, 0.0014, 0.0034 and 0.0039, in good agreement with the measurements of Aufsess. For wave-lengths from 4000 to 5400A γ was less than 0.0004 and was too small to be measured with the length of tubes used.
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