Ixxxii INTRODUCTION. 



TABLE 108. 



Table 1 08. Atmospheric water-vapor lines in the visible spectrum. 



Table io8, prepared by the Astrophysical Observatory at Washington, 

 gives a summary of Hnes in St. John's (1928) revision of Rowland's " Pre- 

 liminary Table of Solar Spectrum Wave Lengths," recorded as of atmospheric 

 water vapor origin. There are more than 400 such lines in Rowland's table, 

 but an abridgment is here made as follows : 



Only lines of intensity " i " or greater are here separately given, but the 

 total number and average intensity of the fainter lines lying between these 

 are inserted. The scale of intensities is such that a line of intensity " i " is 

 " just clearly visible " on Rowland's map ; the H and K lines are of intensity, 

 1,000; Z)i (the sodium line of greater wave length), 20; C, 40. "Lines 

 more and more difficult to see " are distinguished by o, — i, —2, and —3. 



TABLE 109. 



Table 1 09. Atmospheric ivater-vapor bands in the infra-red spectrum. 



The values of Table 109 relate to the transmission of energy in the minima 

 of various water-vapor bands, when there is i cm. of precipitable water in 

 the path through the air. For other amounts of water-vapor, the depths of 

 these minima may be taken as equal to a^, where a is the coefficient taken 

 from the third column of Table 109 and 8 is the amount of precipitable 

 water in cm. in the path. For average conditions in the transmission of radia- 

 tion through the atmosphere, 8 may be determined by the modification of 

 Hann's formula 8 = 2.0(? sec. Z, where e is the vapor pressure in cms. as 

 determined by wet and dry thermometers and Z is the angle which the 

 path makes with the vertical. 



For the use of the transmissions observed in such bands for the inverse 

 process of determining the amount of water-vapor in the atmosphere, see 

 Fowle, Astrophysical Journal, 35, p. 149, 1912; 37, p. 359, 1913. 



TABLE 1 10. 



Table 110. Transmission percentages of radiation through moist air. 



The values of Table no will be of use when the transmission of energy 

 through the atmosphere containing a known amount of water-vapor is 

 under consideration. An approximate value for the energy transmitted 

 may be had if the amount of energy from the source between the wave- 

 lengths of the first column is known and is multiplied by the corresponding 

 transmission coefficients of the subsequent columns of the table. The table 

 is compiled from Fowle, " Water-vapor Transparency," Smithsonian Mis- 

 cellaneous Collections, 68, No. 8, 1917 ; see also, Fowle, " The Transparency 

 of Aqueous Vapor," Astrophysical Journal, 42, p. 394, 191 5. 



TABLE 111. 



Table 111. The spectral distribution of solar radiation and its transmission 

 by the atmosphere. 

 The measured relative intensity of radiation at a given wave length 

 depends not only upon the source, but also upon the prismatic dispersion. 



