j^O. II ATMOSPHERIC OZONE FOWLE II 



and mine at the same stations. He is working at a spectrum place 

 where the coefficient a in the formula, 



/ = /„io-"^' 



is very large, ranging from about i to 4. He is therefore probably 

 working far down on the nearly horizontal portion of a curve such 

 as is indicated in figure 7 where a large change in ozone makes a 

 comparatively small change in the observed spectrum intensity values. 

 On the other hand, in the Chappuis band used by the writer, the 

 coefficient a is so small, about 0.04, that the band is very difficult to 

 observe visually. Therefore we may assume that the writer is measur- 

 ing in a band where a small change in ozone produces a great change 

 in the observed quantity. In other words, for the amount of ozone 

 present in the atmosphere, the Chappuis band is a more sensitive 

 indicator of changes in atmospheric ozone than that employed by 

 Dr. Dobson. 



With these preliminary remarks, attention may be drawn to figure 8, 

 in which recent observations made at Table Mountain with Dobson's 

 apparatus, and reduced by him to cm. ozone ntp. are compared with 

 the writer's results as expressed in areas of the Chappuis band. The 

 average amount of ozone for this interval of time as computed by the 

 preceding table from the writer's results is about 0.23 cm. ntp., while 

 Dobson finds about 0.22 cm. The range of the variation found by 

 the writer much exceeds that found by Dobson, but nevertheless a 

 marked correlation exists between the two series. 



The writer cannot leave Dr. Dobson's work without one further 

 remark about his method. He states,^ " It has been shown that there 

 is a close connection between the amount of ozone in the upper 

 atmosphere and the pressure conditions in the upper part of the 

 troposphere and the lower part of the atmosphere," and states that. 

 " it is remarkable that the ozone situated at so great a height " (40 

 to 50 km., as indicated by the results of Cabannes and Dufay, 30 to 

 40 km. by Dobson himself) should be so closely connected with 

 variations of pressure much lower down." 



Dr Dobson^ uses two methods in his evaluation of the amount 

 of atmospheric ozone. In the first he takes as the general atmospheric 

 transmission coefficient 



' Proc. Roy. Soc. 120A, 251, 1928. 



" Mp^Not. R. A. S. 86, 259, 1926. Proc. Roy. Soc. iioA, 660. 1926. 



