CURRENTS IN MEDITERRANEANS 241 



the Red Sea. Here the ocean waters are of less salinity than those 

 of the mediterraneans, and they flow in on the surface, while the 

 more saline waters from the mediterraneans escape below the sur- 

 face to the oceans, influencing the salinity of the adjoining parts of 

 the sea. In the Straits of Bab-el-Mandeb the surface waters enter 

 the Red Sea with a velocity of 2 to 2^>-4 nautical miles per hour, ex- 

 tending down with diminishing velocity to 130 or 140 meters, below 

 which the outflowing stream ranges in velocity from i to 3 nauti- 

 cal miles per hour. 



An outflowing surface stream, the Baltic Stream, carries the 

 weakly saline waters of the Baltic through the Ore Sound and con- 

 tinues along the Swedish coast of the Kattegat, where it is driven 

 by the prevailing west wind and the rotation of the earth. Its 

 velocity at a distance of 4 to 6 miles from shore is 24 to 48 nautical 

 miles per day in calm weather. Turning westward along the Nor- 

 wegian coast, it may reach a velocity of 80 to 100 nautical miles in 

 24 hours. It normally flows against the prevailing wind, which 

 must reach great strength before it is able to reverse the current 

 even temporarily. This stream has its greatest strength in the 

 spring and early summer months, when the influx of fresh water 

 into the Baltic is at its maximum. 



The currents of the Baltic and its branches are largely dependent 

 on the wind and are further complicated by the tidal currents and 

 the relative amount of influx and evaporation. In the spring 76 

 per cent, of all currents flows westward, owing to the strong influx 

 of land waters and the pronounced east winds. In summer this 

 drops to 60.5 per cent., when evaporation over the Baltic becomes 

 strong and west winds pre\iail, while during autumn and winter 71 

 per cent, and 69 per cent, of all currents of the Baltic flows west- 

 ward. The strength of the outflowing streams may reach 3 to 4 

 nautical miles per hour in the narrows of the western part, or Belt 

 Sea. The Finnish Gulf, which is scarcely separated from the Bal- 

 tic, and has therefore much the structure of a funnel sea, is charac- 

 terized by a westward-flowing surface stream of fresher water and 

 an eastward-flowing compensating stream of greater salinity at some 

 depth below the surface. The Bothnian Gulf, on the other hand, 

 has a more independent circulation in the counter-clockwise direc- 

 tion, and this corresponds to its greater distinctness from the Bal- 

 tic. The current flows into the gulf east of the Aland Islands, and 

 out on the west, except when interfered with by strong winds. 



The circulation of other northern intracontinental seas, like Hud- 

 son Bay, St. Lawrence Gulf and Kara Sea, is a cyclonal one in the 

 counter-clockwise direction. A similar circulation exists in the Red 



