8 SMITHSOXIAX MlSCELLANliOUS COLLECTIONS NOL. 8l 



vapor conies considerably later in the year than that for the area- 

 maximum of the band, yet before the time for its maximum. 



A far more detailed study of the transmission coefficients in the 

 region of this band has been made than was possible with the some- 

 what separated measurements in the spectrum made for the solar- 

 radiation work. Plates for two days were reread and coefficients 

 determined for each maximum and each minimum of the solar lines 

 visible in the observed energy curves (tig. 6, curve a). Unfor- 

 tunately, between deviations 20 and 22, and 27 and 28, such a process 

 was impossible because of instrumental contingencies. The resulting 

 coefificients determined independently for the two days of observations 

 are plotted in curves b and c. This is a useful transformation, result- 

 ing, as it does, in a spectrum, b or c, showing only atmos])heric 

 lines, from an energy curve like a where the solar lines are domi- 

 nant practically to the exclusion of any indication of atmospheric 

 absorptions. 



Assuming for the time being the validity of Bouguer's formula, a 

 further step was taken. Entering figure 2 for the corresponding wave- 

 length wath the transmission coef^cient determined at place 24 from 

 the curve c of figure 6, the amount of ozone was determined. 

 With this amount of ozone, and the transmission coefficients at all 

 the maxima and minima of the curve in figure 2, an ozone band 

 was computed, using the line across the top of the band in curve c 

 of figure 6 as the basis. The result is plotted in curve d of figure 6. 

 The agreement between c and d is better than could be expected and 

 is indeed remarkable. Apparently because the writer is using a purer 

 spectrum than Colange, the deflections in curves b and r are more 

 marked than in curve d, but the agreement in position is satisfactory. 

 Between deviations 26 and 30, the coefficients are too small to expect 

 any accuracy. It seems therefore highly probable that practically all 

 of this band as observed is due to ozone. 



The writer, as already stated, prefers to express the results which 

 follow in terms of a quantity <fairly directly coming from the observa- 

 tions, namely, the amount of energy cut out from the incoming 

 solar energy by this yellow Chappuis band. These results may be 

 approximately reduced to amounts of ozone (ntp.) by using Bouguer's 

 formula Avith the constant determined by Colange (loc. cif.) as 

 indicated by the following table : 



Band area 30 40 1 50 1 60 70 80 [ 90 100 1 cal. X lO" 



Ozone . 90 I . 160 ! . 200 . 230 . 260 I . 290 ! . 320 ! . 350 I cm. ntp. 



