twilight conditions obtain during these months for the greater part of the 24 hours. 

 This cannot, however, be the only cause, as the observations between 22 hours and 

 24 hours during these months are less numerous than between 20 and '2'2 hours. There 

 is thus some indication that during August and September, the afternoon maximum 

 for coloured aurora? may occur later than during the previous three months. During 

 these two months, as well as in March and April, there were very f-\v occnircnrcs of 

 coloured aurora? in the morning hours (only seven in all). 



(d) Diurnal Frequency of " Glow " Aurorce. 



Table 14 shows the daily variation in the occurrence of " Glow " aurora? during 

 the period May 26th to July 31st, using all the available data (not only the observations 

 at even hours). 



TABLE 14. Distribution in Time of " Glow " Aurorse, Cape Adare, 1911. 



The most interesting feature brought out in this Table is that " Glows " are almost 

 equally likely to occur at all hours between 18 hours and 4 hours, at which time a 

 minimum is shown. As glows may be seen and logged independently of any other 

 forms of aurora, it is not strange that no very definite connection is shown with the 

 diurnal frequency of other types. 



Diurnal Frequency and Brightness of Aurorce. 



To ascertain whether the diurnal frequency is dependent upon the brightness of 

 the aurora, Table 15 has been formed, showing the number of occasions (during the 



TABLE 15. Diurnal Frequency and Brightness of Aurora, Cape Adare, March to 



September, 1911. 



Figures for the period May 26th to July 31st are shown in brackets. 



27 



