NO. 8 



WATER-VAPOR TRANSPARENCY FOWLE 



25 



distribution of energy in the spectrum here observed with the Nernst 

 lamp at 2.200° K. is indicated, and this may be regarded as a measure 

 ■of the " weights " of the different parts in producing the absorption 

 vakie here given. If instead of a Nernst glower the sun were 

 observed, the upper part of the table would have even greater weight, 

 while with the earth as a radiator the lower part should have a 

 greater weight. The relative weights in the earth's 'case are given in 

 the last column and the absorption value in the footnote to the table. 



Table 4.^Absorption by Water Vapor, 1.3 to 8.0 fi 



Band 



n 



X 



T> „ c Relative energy 



R^"8e of I . ,^ j,,,3«f. 



wave-length ,1 ^ radiator 



Percentage absorbed 



1.3 to I, 



1-75 



2.2 



4.0 



/3 

 2.2 

 3.2 

 4.0 



4-9 



2300 

 2150 

 2400 

 1050 

 640 



r. • •. ui i ■ I Relative energy 



Precipitable water in cm. i 287° K. Black 



radiator 



o.oc8 



6.1 



13.6 

 23.6 

 21.7 

 32.5 



18 

 29 

 41 

 37 

 50 



I 



38 



418 



* These figures give the percentage of radiation from the Nernst lamp (.2,2oo''-30o° K.) 

 absorbed in the band Z (4.9 to 8.0M) and in the whole region 1.3 to 8.0M. The correspond- 

 ing figures obtained by means of columns 4, 5, and 6 for a distribution of energy of a 

 "black-body radiating at the temperature of the earth (287° K.) to space (0° K.) would be 

 43 and 42 per cent for 0.008 cm. ppt. H^O and 76 and 74 per cent for 0.082 cm. ppt. H^O. 



ABSORPTION DOWN TO i6 n 

 \^'ith the 6o°-prism spectroscope used in the work just detailed, 

 the energy even at 9 ^u, had become almost too feeble for accurate 

 measurement. From 10 fi to 16 /x recourse was necessary to the 

 smaller dispersion and consequently greater intensity in the spectrum 

 formed by a 15° rock-salt prism. The reduction of the correspond- 

 ing observations brought many more difficulties as the detailed dis- 

 cussion coming" will show. 



