SEA WATER 229 



motion are varied, and among these the polar ice, the sun's 

 heat, the trade winds and the rotation of the earth all 

 play their part. 



This current is really only a portion of a system of currents 

 in continuous circulation in the Atlantic Ocean, a system 

 which cannot be said strictly to begin or end anywhere. 

 We will however confine ourselves here to the North 

 Atlantic. 



In the region just north of the equator the surface waters 

 are warmed by the fierce heat of the tropical sun and their 

 salinity is raised by constant evaporation. Upon these 

 warm saline waters are continually blowing those per- 

 sistent north-easterly winds known as the " North-east 

 Trades." Their action aids a natural tendency of the 

 surface waters to move in an easterly direction towards 

 the north coast of the South American continent as the 

 North Equatorial Drift, which flows on into the Caribbean 

 Sea and Gulf of Mexico. Here the waters become piled 

 up so that the surface level is raised above that of the 

 ocean water outside the islands of the West Indies in the 

 Sargasso Sea. Under such conditions the water must 

 flow somewhere in order to maintain its equilibrium. 

 Its only place of egress is through the Florida Straits and 

 here it issues as the mighty Gulf Stream, the actual current 

 through the straits being sometimes known as the Florida 

 Stream. From here the Gulf Stream runs in a northerly 

 direction along the coast of America at a speed of about 

 four knots (Plate 85). 



Owing to the rotation of the earth there is a tendency 

 for any moving particle to be deflected to the right. This 

 action is felt by the Gulf Stream and it moves northwards 

 with an increasing trend towards the right or east, so that 

 by the time it has reached latitude forty degrees north 

 it is flowing due east across the Atlantic. At this point 



