240 PRINCIPLES OF STRATIGRAPHY 



The currents of the Arabian Sea and the Bengal Bay are clearly a 

 part of the circulation of the Indian Ocean, while the circulation 

 of the China Sea is in part a branch of the North Equatorial cur- 

 rent of the Pacific. In general, the circulation of the mediter- 

 raneans is a cyclonal one, and it becomes more individualized the 

 more the water body is separated from the oceans adjoining. 



The Roman Mediterranean, which is connected with the At- 

 lantic only by the narrow Gibraltar Straits, nevertheless receives a 

 small branch of the northern West-wind drift. This stream, 

 though subject to modification by local winds, is recognizable 

 throughout, and influences the- migration of the sands of the bot- 

 toms and coasts. It passes eastward along the north coast of Al- 

 giers, through the narrows between Tunis and Sicily, with a veloc- 

 ity of 5 to 10.5 nautical miles per day, and south of Malta toward 

 Barca (Africa), causing eddies in the Gulf of Sidra. turning north- 

 ward on the Syrian coast, and westward on the south coast of Asia 

 Minor, around Crete into the Ionian Sea, then north along the Dal- 

 matian, and south along the east Italian coasts, making a counter- 

 clockwise circulation in the Adriatic. In the Tyrrhenian Sea it con- 

 tinues northwestward, then west in the Ligurian and southwest 

 along the Spanish coast, thus completing the counter-clockwise cir- 

 culation. This circulation takes place largely under the influence of 

 the local winds, and is not always constant. 



Both the Adriatic and /Egean seas have practically independent 

 circulations in a counter-clockwise direction, and a similar circula- 

 tion exists in the Black Sea, though a part of the water moving 

 along the west coast of this body passes out as a strong stream 

 through the Bosphorus, the Sea of Marmora, and the Dardanelles 

 into the ^gean Sea. To compensate this outflow, a deeper lying 

 current enters from the ^gean and the Marmora Sea. At Con- 

 stantinople the outflowing stream of the Bosphorus has a velocity of 

 123 cm. per second at the surface, and rapitlly decreases to nothing 

 at 20 meters' depth. At 25 meters' depth the inflowing stream is at 

 its maximum with a velocity of 73 cm. per second with moderate 

 diminution downward, its strength at 40 m. depth being still 43 cm. 

 per second. Makarofif has estimated that the outflowing stream car- 

 ries 10,530 cb. m. per second, while the inflowing carries only 5,700 

 cb. m. per second. This makes a yearly deficit of 152 cb. km., the 

 excess carried out over the inflow, and this has to be replaced by the 

 annual precipitation and afflux of water from the drainage basin. 

 A similar out- and influx take place through the Straits of Kertch 

 between the Sea of Azov and the Black Sea. Just the reverse mo- 

 tion is seen at the mouth of the Roman Mediterranean and that of 



