SALTNESS OE THE SEA. 



?3 



Forchliaminer liave reduced this proportion to 34-40. Besides, al- 

 most all the analyses, which up to the present time have been made 

 of sea-water, confirm the general opinion of chemists, that the re* 

 lative proportion of the matters dissolved is the same in all seas. 

 The quantity of common salt (chloride of sodium) dissolved in sea- 

 water, is always a little more than three quarters (75 786) of the 

 total mineral matter held in solution. 



Fig. 9.— Comparative saltness of Seas. 



In the north tropical Atlantic, on the coasts of the Sahara and 

 of Morocco, where the sea receives no tributaries, and where, on the 

 other hand, the evaporation is very rapid, the average of oceanic salts 

 is nearly 38 parts in 1000. In mid-ocean, and more especially in the 

 neighbourhood of America, where the water of many great rivers 

 mingles with that of the sea, the saltness is less by one, two, and even 

 three thousandths ; but it is generally greater in the tepid waters 

 of the great current called the Gulf-stream, which crosses the Atlantic 

 obliquely. The proportion of salts contained in this current always 

 exceeds 35 thousandths,* while the water that flows from the pole 

 towards the equator by Baffin's Bay, contains only about 33 thou- 

 sandths. It is to the enormous accumulation of ice, that these cur- 

 . rents owe the slightly less saltness of their waters. The quantity .of 

 * See below, the chapter headed, Currents. 



