OCEANIC CONTROL 'OVER CLIMATE 33 



Accordingly the warmer of two adjacent geo- 

 graphical areas will be covered by an ascending 

 air current and the barometer in it will indicate 

 low pressure ; it will be a " low pressure area." 

 Conversely, the colder of two adjacent areas 

 will be covered by a descending air current 

 and will be a " high pressure area." There- 

 fore in summer land is covered by a low- 

 pressure area ; it is said to be covered by 

 a cyclone, while the prevalent winds will 

 blow inward from the sea. Land in winter 

 is covered by a high pressure area, and is 

 said to be occupied by an anticyclone, and 

 the prevalent winds will blow outward to the 

 sea. This change of the inward and outward 

 winds, or, as it is called, this monsoonal 

 change, may take place daily in the case of a 

 small island ; but when the change is seasonal 

 and is due to the differential heating of great 

 oceans and continents, then we have seasonal 

 monsoons. In these cases the winds are 

 reversed twice a year, as with the monsoons 

 that dominate the climate of India and northern 

 Australia. We can, therefore, understand why 

 countries, which are subject to monsoonal con- 

 ditions, receive most of their rainfall in the 

 summer ; for then, the winds coming in from the 

 sea, bring with them a great supply of moisture, 

 which falls as rain. The incoming wind does not 

 drop its rain at once ; for as it passes from 

 the colder ocean to the warmer land, the air is 

 warmed, and its capacity for holding moisture 



