24 THE OCEAN. 



cold water whicli flows from tlie Antarctic Pole towards the south of 

 Africa and America, contains likewise less saline matter than the seas 

 of the temperate and equatorial zones. 



With regard to basins almost enclosed, like the Mediterranean, the 

 Caribbean Sea, and the Baltic, the saltness ought evidently to be 

 greater or less there than in the ocean, according as the evaporation 

 is in excess of or is inferior to the fresh water brought by the 

 rivers and the clouds. In the Mediterranean, the loss in evapora- 

 tion being more considerable than the contributions of fresh water, 

 the saltness ought to increase in consequence, and the liquid mass 

 would constantly diminish, if a current setting in from the Atlantic 

 through the Straits of Gibraltar did not restore the equilibrium. 

 While the less saline waters of the ocean thus penetrate into the 

 Mediterranean flowing along its surface, a submarine counter-cur- 

 rent, composed of heavier and Salter water, flows deep below in an 

 opposite direction, and mingles with the waters of the Atlantic, 

 which contain less salt. The mean saltness of the Mediterranean is 

 nearly 38 thousandths, and even exceeds 39 thousandths on the coasts 

 of Tripoli, where the parching winds of the Libyan desert blow. 



In like manner the Caribbean Sea seems to present a somewhat 

 high relative saltness because of an excess of evaporation over the 

 contribution of fresh water ; but the contrary happens in the Gulf of 

 St. Lawrence, in the North Sea, and above all in the Baltic and the 

 Euxine. The saltness of the North Sea is in different parts from 30 

 to 35 thousandths, while that of the Baltic, a shallow sea into which 

 60 many rivers flow, and where the least wind disturbs the waters,* 

 does not quite amount to five thousandths ; in the port of Cronstadt 

 it is not even two-thirds of a thousandth, which is almost fresh 

 water. As to the Black Sea, it preserves, even more than the Baltic, 

 the character of a gulf of the ocean, for the average saltness is about 

 half that of the Atlantic. 



These diflerences of salinity between the cent;^'al basin of the 

 Atlantic and its tributary seas are not in themselves astonishing ; 

 but we do not j^et know why the South Sea and Indian Ocean contain 

 less saline matter in their waters than the Atlantic, unless the enor- 

 mous quantity of Antarctic ice explains this diflerence. While the 

 latter has a saltness of about 36 thousandths, the water of the Pacific 

 has less by nearly one thousandth, and the Indian Ocean contains no 

 more than 35 thousandths of chemical substances. The Atlantic, 

 however, receives a greater quantity of fresh water than the other 



* Von Sass, Zeitachrift fur die Erdkunde. 



