NO. 1 I 



ATMOSPHERIC OZONE FOWLE 



25 



which are an important feature of the auroral spectrum, are not 

 usually present. 



Rayleigh's observations (tig. 13) apparently indicate an annual 

 march in the intensity of this green line with two maxima — the 

 smaller maximum occurring nearly contemporaneously with the single 

 maximum in the ozone march, the larger with the ozone mininnun. 

 In the southern hemisphere, as with ozone, the months of the occur- 

 rence of these maxima are reversed but, of course, not the season. 



Omitting observations made at Clarcmont which Rayleigh considers 

 faulty, together with those for some stations with only few observa- 



'!(.. 13. — Lord Rayleigh's observation on Aurora green line. The gap in the 

 northern hemisphere results is due to the impossibility of observations 

 during these months in England because of twilight. 



tions the following table was formed. The values given relate to a 

 comparison of night sky observations with a standard source of light. 

 For details the reader is referred to Lord Rayleigh's article. The 

 scale units are such that in passing up one unit the intensity is 

 multiplied by the anti-logarithm of o.i or 1.259; three steps on the 

 scale are equivalent to a factor (1.259)° ^^ approximately a doubled 

 intensity. The presentation is dilTerent froin that of Rayleigh so as 

 to separate the stations of the northern and southern hemispheres. 

 It indicates that the auroral line averages of greater intensity in 

 the northern hemisphere while the parts of the spectrum on either 

 side show no such difference. 



