Quantitative measurements on the absorption coefficient of air have been made for about three hundred and fifty points between 380 and 1600A. Because of difficulties in maintaining a constant intensity with extreme ultraviolet light sources, it was necessary to use a many-line spark source rather than a continuous spectrum, with the result that much of the fine structure of the absorption bands has been lost. Photographic measurements with oiled plates show strong absorption between 1600A and 1300A, a quite transparent region between 1300A and 1000A, and a very highly absorbing group of bands at the shorter wave-lengths. Although these bands below 1000A are poorly resolved, a wealth of fine structure is evident.
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