38 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



Certain common features stand out clearly in all these charts. 

 First, in the equatorial belt, except possibly over parts of the Pacific 

 Ocean, the pressure is lov^er than normal at the time of maximum 



Fig. 24. — 11.3-year period in pressure = ^ of 22.6 years. Departures at time 

 of maximum of solar period of same length. 



solar activity in each period. Second, in middle latitudes of the 

 Southern Hemisphere there is a tendency to a belt of pressure above 

 normal which cannot be well outlined on account of insufficient 



Fig. 25. — 5.65-period in pressure = i of 22.6 years. Departures at time 

 of maximum of solar period of same length. 



observations. Third, in the Northern Hemisphere in high latitudes 

 there is a tendency for the departures to form centers of positive and 

 negative departures, usually two centers of positive departure, and 



