ATMOSPHEEIC ELECTRICITY IN HIGH LATITUDES. 



85 



Table XVI. gives the mean and maximum values of the activity for each month. 

 From it the yearly course is seen to consist of two periods. During the first, 

 extending from the beginning of September to the end of February, the radio-activity 

 is constant and very high. During the other months the activity is much lower (less 

 than half) and not quite so constant. The maximum falls in midwinter and the 

 minimum in midsummer. A distinct daily period is also shown : the maximum falling 

 in the early hours of the morning and the minimum about midday. 



Table XVII. shows the effect of temperature on the radio-activity. It is interesting 

 to notice that from the results for the whole year the temperature appears to have a 

 very marked effect on the radio-activity ; but when each month is taken by itself, 

 the effect is not apparent at all. It would appear from this that temperature only 

 plays a secondary part in determining the amount of activity in the air. 



TABLE XVII. Radio-activity and Temperature. 



The relative humidity appears to have a very large effect on the radio-activity, for 

 not only can its influence be seen when the year is taken as a whole, but it is very 

 apparent in each separate month with the exception of February. 



TABLE XVIII. Radio-activity and Relative Humidity. 



