36 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. ']'/ 



defect of pressure over the oceans, both north and south of the 

 equator, is now well defined and a belt of excess pressure extends 

 along- the equator except across the Atlantic, Africa, and a part of 

 the Indian Ocean. In this region the defect is very slight and it is 

 possible that a larger number of observations would show that it 

 occupied a much smaller area than shown. The areas of maxima are 

 now very near the equator, being between o° and io° latitude south 

 of the equator, and between 15° and 30° north of the equator. In 

 the north there is an excess of pressure north of the 60th parallel, 



Solar radiation one percent below normal — July 1913, 



Fig. 30. 



probably due to a southward extension of the polar anticyclone, or 

 area of high pressure normally found near the pole. 



The succession of maps brings out clearly a steady progress of the 

 excess of pressure over the northern oceans from about 60° N. with 

 solar radiation 2 per cent above normal to about 20° N. with solar 

 radiation 2 per cent below normal. 



The area of greatest defect in North America moves from northern 

 Canada in about latitude 64° N., southeastward to the Middle Atlantic 

 in about latitude 45° N. The deficiency in Asia appears to move 

 westward to Europe. In the southern hemisphere the excess of 

 pressure in about latitude 50° S. appears to move equatorward with 

 decreasing solar radiation, followed by a deficiency of pressure which 

 advances from a high latitude with high solar radiation to the 

 latitude of about 30° S. with very low solar radiation. 



