24 



Mr. R. M. Deeley on the 



from the high-pressure ridge in opposite directions, but on 

 the south side it blows against the surface temperature 

 gradient. In July in Asia there is an area of low pressure, 

 whilst over the Indian Ocean in 30° S. lat. the high pressure 

 area persists. The Wet Monsoon blows from this high 

 pressure area into Asia, in agreement with the temperature 

 gradient, but is deflected to the west before it crosses the 

 equator and to the east on its way to India. 



The barometric pressures over the Atlantic are shown in 

 fig. 9. Here, except in the extreme north, the pressure 



Fio». 9. 





Latitude 



1 



o 

 to 



,5 



30-O 

 29-5 

 29C 









/ 



^*3- 



^\ 



\ 











1 



lj 





Longi 



tude 20 



°W 











/ 



// 



/ 



































S. 80° GO" 4-0° 20° 0° 20° 4-0° 60° SO" N. 





distribution is much the same in both hemispheres ; but the 

 pressures are higher in July than in January. This arises 

 from the fact that the greater portion of the land area of the 

 earth is in the Northern Hemisphere, and during the summer 

 of this hemisphere the land areas as a whole are warmer 

 than the oceans, and the air is to some extent transferred 

 from the land to the water-covered areas. Here we have a 

 further reason for believing that the main circulation of the 

 atmosphere is due to temperature gradients. 



The temperature and pressure curves that have been de- 

 scribed show clearly that the great land areas in the Northern 

 Hemisphere have a great disturbing effect upon the atmo- 

 spheric circulation in that hemisphere. In the Southern 

 hemisphere the curves show a much more simple state o£ 

 matters, due no doubt to the tapering of the southern con- 

 tinents and the concentric position with respect to the earth's 

 axis the Antarctic continent occupies. 



In the Southern Hemisphere the curves show that we 

 have: — 1st. A low pressure belt along the equator. 2nd. A 

 high pressure belt along latitude 30° S. 3rd. A deep low 



