Ixxxiv 



INTRODUCTION. 



These computations take account of the depletions of solar radiation by 

 scattering only. We now proceed to compute the energy in the total solar 

 spectrum after passing through dust-free air containing the amounts of at- 

 mospheric moisture specified, and with the sun at the distances from the 

 zenith indicated. 



The wave lengths given in column 2 do not cover the entire range of 

 wave lengths included in the solar spectrum. It is therefore necessary to 

 apply a correction to the measured energy so as to include the energy not 



Air Mass. m. (Pressure -760 cm) 

 1.0 20^ 



30 



40 



measured. Abbot's ^ method of determining these corrections has been 

 followed in computing the corrections for u. v. (ultra-violet) and i. r. (infra- 

 red) energy not measured, which are given in the lower part of Table iii. 

 The absorption by water vapor in the great water vapor bands in the infra- 

 red (w. V. absorption) had been computed by the method developed by Fowle.- 

 Finally, Fowle has computed for this table the absorption by the permanent 

 gases of the atmosphere. 



The relative energy in different parts of the solar spectrum may now be 

 determined by summing up the energies at different wave lengths, giving 



1 Abbot, C. G. Smithsonian Solar Researches. Gerland's Beitrage zur Geophysik, 

 Bd. XVI, Heft 4, pp. 344-353, 1927. 



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

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



