12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



the transmission coefficients, which in this case define the ozone area. 

 This is shown by a comparison of the March 24 value in this set of 

 eight with the value for this same day as given above, which was 

 determined from the transmission coefficients at all the points chosen 

 in the above work. The former value is 2.8 mm., while the latter 

 3.9 mm., and the latter is, as stated above, believed to be a satisfactory 

 determination. The cause of this discrepancy appears to lie chiefly in 

 the fluctuations in the few observed transmission coefficients. To 

 summarize : The use of the few single values of the transmission 

 coefficients as regularly determined in the solar-constant work only 

 suffices to define an area which gives the approximate amount of ozone 

 and is not ordinarily competent to show the fluctuations from day to 

 day within an error small compared to the fluctuations. 



SUMMARY 



The transmission of ozone for visible light has been determined 

 from spectrobolometric data using the solar spectrometer of the 

 Smithsonian Institution at Table Mountain, Calif., with the sun as 

 the source and introducing chemically determined quantities of ozone 

 in the path of its rays. The results are in close accord with the labora- 

 tory results of Colange. Using the results of this study the amount 

 of ozone over Table Mountain for one typical day as an illustration 

 has been determined. By an abbreviated method, using only the trans- 

 mission coefficients normally measured in the regular solar work, the 

 value for the ozone over Table Mountain has been determined for a 

 series of eight days. The mean of these eight days presumably gives 

 a good value for the mean amount of ozone, but this abbreviated 

 method is not ordinarily sufficient to show the fluctuations in the ozone, 

 since the possible error in a single determination is of the order of 

 the fluctuations. The mean value for the eight days dififers but about 

 6 per cent from the mean value for the same days determined by the 

 method of Dobson. It is very interesting that the holographic method 

 depends on ozone absorption in the yellow, while Dobson's photo- 

 graphic method employs the ultraviolet ozone absorption. 



The author wishes to express his sincere thanks to Dr. C. G. Abbot 

 for suggesting the problem and for his continued interest and help 

 throughout the work, and to Mr. J. A. Roebling for a financial grant 

 which made the work possible. The efforts of a number of people 

 have contributed directly to the completion of this work, especially 

 Mr. Alfred F. Moore, Mrs. Beatrice J. Wulf, Mr. Fred Greeley, and 

 Mr. George Cox. The author is grateful to the members of the 

 Smithsonian Astrophysical Observatory for their frequent kind 

 assistance. 



