8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



was desirable to have an equal distribution of the observations 

 throughout the months in order to study and to eliminate seasonal 

 influences. If, however, only those months had been used in which 

 both values were present, the main conclusions which follow would 



Table 3. — Mean Departures of Pressure from Normal in Millibars ivith High 



Solar Activity 



Winter HaU'-Year 



Summer Half- Year 



Year 



Values in parentheses are interpolated from a synoptic chart (polar projection). 



not have been greatly impaired, although the quantitative values 

 would have been different. 



The monthly values of pressure for the months when solar activity 

 was above normal were separated into zones of io° of latitude, 

 namely all between 80° N. and 70°N., between 70° N. and 6o''N., etc. 

 Because the stations were not equally distributed, but were mostly 



