118 THE OCEAN 



issuing from the Mediterranean as the source 

 of the remarkably high temperature and 

 sahnity overspreading the North Atlantic. 

 At 700 and at 800 fathoms the same influence 

 is traceable in the high densities recorded to 

 the east of the Azores and to the west of 

 Gibraltar. 



Prevailing Winds. — ^The prevailing winds of 

 the globe in their direct and indirect effects 

 taken in conjunction with the configuration 

 of the land-masses are, however, the most 

 powerful agents in originating, giving direction 

 to, and maintaining the circulation of oceanic 

 waters. They undoubtedly originate ^nd 

 maintain the surface currents of the ocean, 

 and the influence of these currents is, through 

 friction, felt to a depth of evidently several 

 hundred fathoms. In intertropical regions 

 the prevailing trade-winds drive the surface 

 currents westwards to the eastern shores of 

 the continents, where accordingly a greater 

 depth of warm water is found occupying the 

 upper layers of the ocean than elsewhere. 

 Except where the rainfall is abnormally heavy 

 this water not only is very warm but has 

 acquired from evaporation a salinity much 

 higher than the general average of the ocean. 

 These areas of high surface temperature and 

 high salinity are found represented at all 

 depths down to the bottom, with a tendency 



