176 A TEXTBOOK OF OCEANOGRAPHY 



west side of the sea a strong and steady current in a southerly 

 direction. On the Asiatic side a northerly current prevails. 

 From the Dardanelles there is a strong outward current of 

 low salinity which takes a south-westerly direction. This 

 Dardanelles water is turned to the north (right) by the earth's 

 rotation, which, combined with the prevailing north wind, 

 drives it in a south-westerly direction around the islands of 

 Imbros and Lemnos and on to the Eubœan coast. This current 

 is very strong off Andros and Tenos, where it attains an hourly 

 velocity of from i'5 to 2 miles. Afterwards it takes a more 

 southerly trend past Cape Malia, then through the Straits of 

 Cervi to the west. 



The currents in the Bosporus, Sea of Marmora, and the 

 Dardanelles, run out into the ^gean Sea. With strong south- 

 westerly winds there is, however, a feeble current in the reverse 

 direction. In the Dardanelles the mid-current runs at from 3 

 to 5 miles per hour. Thèse currents are due to the différences 

 in density between the Sea of Marmora and the -^gean. In 

 addition to this surface current, there is a counter-current in 

 the reverse direction below 10 to 30 mètres. 



The currents in the Bosporus were known to the ancients. 

 They are very strong, and there is a daily periodicity, with 

 a minimum at night and a maximum a few hours after 

 midnight. There is also a yearly periodicity due to changes 

 in level in the Black Sea, which is highest in spring. The 

 surface current hère has a salinity of 20 per mille, the deeper 

 counter-current 36 to 38 per mille (yEgean water). 



The currents in the Black Sea change with the wind. The 

 gênerai tendency on the west side is to the southward, and 

 thence through the Bosporus, though only a portion of the 

 current goes through, the remainder continuing on to the east 

 and forming a counter-clockwise current through the whole 

 area. 



The bottom currents of the Black Sea hâve been investi- 

 gated by Wrangel and Spindler. 



The entry of sait water into the Black Sea through the 



