216 Atmospherical Radio-activity in High Latitudes. [Feb. 3, 



The only meteorological element which appears to have a direct 

 influence on the atmospherical radio-activity is the amount of cloud. 

 To show this I have divided the observations into three classes : 1st 

 Sky clear, or nearly so ; 2nd Detached clouds ; 3rd Sky completely 

 overcast, and taken the mean for each class. The results are given in 

 Table VI. 



Table VI. — Radio-activity and Clouds. 



Clouds. 



Clear sky. 



Detached 

 clouds. 



Completely 

 overcast. 



No. of observations . . . 



18 



26 



27 





130 



107 



76 





432 



384 



198 



There does not appear to be any close connection between the 

 aurora and the radio-activity, the greatest value of the radio-activity 

 having been obtained when no aurora was visible. 



During the whole time these observations were being taken the sun 

 did not rise above the horizon. The time used was mid-European, 

 local mean time being 42 minutes ahead. 



The place of observation is 140 metres above sea-level. The ground 

 for a hundred miles round is hard frozen to a great depth and covered 

 with a coating of snow the average depth of which is over 2 feet. 

 Sudden changes in radio-activity are sometimes observed to take place, 

 as, for example, on December 17, when with a rising barometer the 

 activity rose for a few hours from the low value of 66 to the 

 exceptionally high one of 384. There is some difficulty in reconciling 

 these observations with Elster and Geitel's view that the activity is 

 entirely due to a diffusion of a radio-active emanation from the soil. 



