OCEANIC CIRCULATION 123 



called the south-west monsoon. In winter 

 the pressure is high (anticyclonic) over the 

 same area in the interior of Asia, and winds 

 blow out from the land, strengthening the 

 north-east trade-wind, which is called the 

 north-east monsoon. The permanent winds 

 are thus influenced and their direction altered 

 in the northern part of the Indian Ocean, and 

 similar effects though not so marked are 

 found in the neighbourhood of all continental 

 masses. In the great Southern Ocean the 

 expanse of water is practically unbroken by 

 continental land, and the westerly winds blow 

 regularly all the year round, like the trade- 

 winds ; the belt between lat. 40° and 50° S. 

 is called by sailors the " roaring forties " 

 because of the strength and constancy of these 

 " brave west winds," the barometer being 

 permanently low throughout this region, 

 while all observations indicate that a per- 

 manent anticyclone rests upon the Antarctic 

 continent to the south. 



In the anticyclonic areas the movement 

 of the air in the northern hemisphere is in the 

 direction of the movement of the hands of a 

 clock (clockwise), and in the southern hemi- 

 sphere in the opposite (counter-clockwise) 

 direction. 



Surface Currents. — ^The general movements 

 of the surface waters correspond with the 



