NO. 9 DETERMINATION OF OZONE WULF 3 



of the solar energy will be cut out by the ozone as is illustrated in 

 Figure i, which represents a normal spectral energy curve roughly 

 similar to that of the sun showing the approximate area removed by 

 the atmospheric ozone in the visible. 



However, the actual observing of this reduction of intensity must 

 be made on the complicated solar curve as shown in Plate 2. which is 

 composed of a series of typical holograms notched by many Fraun- 

 hofer absorption lines. The discontinuities in the curves are due to 

 the insertion of rotating sectors in the path of the solar beam to cut 

 down the intensity in the regions of great intensity, to values such 

 that the galvanometer deflections will still fall upon the photographic 



Fig. I. — Spectral energy curve of black radiator, approximating that of 

 the sun, showing the atmospheric ozone absorption in the visible. 



plate on which these deflections are being continuously recorded in 

 the form of these curves. In addition, at two points a shutter is 

 inserted for the purpose of determining the base line, that is, the line 

 of zero deflection. Owing to the scattering of the rays by the earth's 

 atmosphere the apparent maximum of the sun's intensity is shifted 

 to longer wave lengths. The strong atmospheric absorption in the 

 deep red is conspicuous, while over the region of ozone absorption 

 chiefly the Fraunhofer lines are in evidence. 



In spite of these complexities, however, comparison of two holo- 

 grams, one without ozone in the cell and one with ozone, should show 

 the reduction in intensity caused by the ozone, providing weather 

 conditions remained sufficiently constant between the two. If, for 

 example, we were to take the ratio of ordinates at corresponding 

 points on two such holograms under ideal conditions this ratio should 



