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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 68 



■ (3) ABSORPTION BY LIQUID WATER, WAVE-LENGTHS I TO 18 ^ 



In figure 17 are given data obtained by Rubens and Ladenburg ^ 

 with the use of two bubble films, one (b) 3.09 fx thick and containing 

 10 per cent glycerine, the other (a) 1.89 fx thick and containing 25 

 per cent glycerine. The maxima in both curves at 7.0 and 9.5 [x 

 are probably due to glycerine. 



Fig. 17. — Absorption of radiation by liquid water films. Rubens and 

 Ladenburg, Verb. D. Phys. Gesell. 11, p. 16, 1909. Abscissae are wave-lengths 

 in microns (m). Ordinates are percentage absorptions, a, film 0.00789 mm. 

 thick; b, 0.00309 mm. thick. 



The main laboratory results of this research, done to obtain quan- 

 titative measures of the transparency of aqueous vapor for radia- 

 tion, have just been summarized. Below the great water-vapor band 

 6 to 8.5 fx, which is very strong even with the small amounts of vapor 

 present in the laboratory, the great transparency of the region 

 stretching from 9 towards 14 fx was surprising and absorption effects 

 there were scarcely perceptible. The total depletion of energy by 

 the great carbon dioxide band 14 to 15.5 /x and the decreasing trans- 

 parency of the rock-salt prism employed prevented results for longer 

 wave-lensfths. 



F. ATMOSPHERIC TRANSMISSION OF SOLAR ENERGY. 9 TO I 5 /A 



The unexpected transparency for wave-lengths just longer than 

 9 IX led to direct observations of solar energy through paths in air 

 which increased with decreasing altitudes of the sun. A range of 



^ Verb. Deutschen Physikaliscben Gesellschaft, ii, p. i6, 1909. 



