MISCELLANEOUS TABLES. Ixxxiii 



Usually, a dispersion coefficient is used to reduce the intensities to what they 

 would have been had the dispersion been the same at all wave lengths, but 

 in Table iii it is that of the ultra-violet glass prism employed by the Astro- 

 physical Observatory of the Smithsonian Institution in making Solar radia- 

 tion measurements. Column i gives the deviation from w^ in minutes of arc 

 at which the energy was measured. Column 2 gives the corresponding wave 

 length. Column 3 gives transmission coefficients, aax, for pure dry air at 

 760 mm. pressure, with the sun in the zenith. They have been computed by 

 means of Rayleigh's equation as modified by King.^ Fowle's ^ values of a^^X' 

 the transmission coefficient for that amount of atmospheric water vapor 

 which if precipitated would produce a layer of water one centimeter thick, 

 have been employed to compute the transmission of solar radiation through 

 moist air. Column 5 gives what Abbot ^ considers the most reliable value for 

 the relative energy outside the atmosphere, ^ox, at the wave lengths corre- 

 sponding to the deviations of Column I. 



The data in the upper part of Columns 6, 7, and 8 have been computed by 

 means of the factors shown in their respective headings. They give the energy 

 distribution with the sun in the zenith and atmospheric pressure of 760 mm., 

 column 6 with no moisture present, and columns 7 and 8 with sufficient mois- 

 ture to produce a layer of water i.o cm. and 2.0 cm. thick, respectively, if 

 precipitated. 



Fowle * has shown that for average conditions the precipitable water in the 

 atmosphere above a given place may be approximately determined from the 



—h 



equation iv = 2.;^c 10 22000 , where e is the surface water vapor pressure in 

 centimeters and h is the altitude of the place above sea level, in meters. The 

 Aerological Division of the U. S. Weather Bureau is developing equations 

 that more accurately express the relation between surface vapor pressure 

 and the water-vapor content of the atmosphere, utilizing for this purpose its 

 valuable accumulation of free-air data. It's results, which are approaching 

 completion, will probably be published in the Monthly Weather Review during 

 the current year. 



Similarly, the data in the upper part of columns 9 and 10 have been 

 computed for the sun at zenith distances 60 and 70.7 degrees, and the moisture 

 content of the atmosphere equivalent to i.o cm., and 3.0 cm., of precipitable 

 water, respectively. 



1 King, Louis Vessot. On the scattering and the absorption of light in gaseous media 

 with applications to the intensity of sky radiation. Phil. Trans. Roy. Soc, London, A. 212, 



p. 375, 1919. 



- Fowle, F. E. Water vapor transparency to low-temperature radiation. Smithsonian 

 Misc. Coll., vol. 68, no. 8, 1917. 



3 Abbot, C. G., and others. The distribution of energy in the spectrum of the sun 

 and stars. Smithsonian Misc. Coll., vol. 74, no. 7, 1923. 



* Fowle, F. E. Atmospheric transparency for radiation. Monthly Weather Review, 

 vol. 42, pp. 2-4, 1 914. 



