84 



ME. GEORGE C. SIMPSON ON THE 



repeat them the following month, and so on. This was done for the whole year with 

 the exception of the summer months, when observations were made alternate weeks 

 instead of alternate months. Besides the three observations during the day, for one 

 week out of every four I continued the observations during the night, observing 

 between the hours of 3 and 5 A.M. 



In order not to interfere with my other observations, the observations of the radio- 

 activity had to fit in between them, and the following times were chosen as being 

 the most convenient : Night observation from 3 to 5 A.M. ; morning observation from 

 10 to 12 A. M. ; afternoon observation from 3 to 5 P.M. ; and evening observation from 

 8.30 to 10.30 P.M. In this way it proved possible to get a good idea of the yearly 

 and daily course of the radio-activity. From the 420 separate observations the effect 

 of the different meteorological conditions have been obtained. 



As the value of the radio-activity varied very greatly from month to month, in all 

 the following tables each month is treated by itself, and then the whole year treated 

 in a separate column. 



TABLE XVI. Kadio-activity. 



* For the observations of this month set out in full detail see 'Boy. Soc. Proc.,' vol. 73, p. 209, 1904. 



