56 THE OCEAN 



34 per thousand), on the other hand, occur 

 in the eastern part of the northern Indian 

 Ocean, Bay of Bengal, Malay Archipelago, 

 and western part of the China Sea, where 

 the rainfall is extremely heavy and evaporation 

 low. In the equatorial regions of each ocean 

 there is a band of comparatively fresh water, 

 and fresh zones surround the melting ice in 

 the Arctic and Antarctic regions. Where 

 rivers enter the ocean the lighter river-water 

 tends to float on the surface, and its freshening 

 influence may be detected at great distances 

 from the land, and when much detrital 

 matter is associated with this river-water the 

 detritus in falling to the bottom carries with it 

 some fresh water, and thus dilutes the under- 

 lying salt water to great depths. The effect 

 of rivers is well shown in the case of the 

 Baltic and Black Seas, where the salinity 

 does not exceed 20 per thousand, and the Gulf 

 of Guinea, where the salinity is less than 32 

 per thousand. 



In permanent anticyclonic regions of the 

 great oceans the salinity is very high (in the 

 Sargasso Sea region of the North Atlantic it 

 may attain 37-9 per thousand) ; out of these 

 areas winds blow in all directions, and the 

 drain caused thereby is compensated for by 

 vast descending currents of very dry air, 

 evaporation being necessarily very great. 



