THE SALTS OF TUE SEA. 241 



brought dowu into the Red Sea. Its salts come from the ocean, 

 and the air takes up from it, in the process of evaporation, fresli 

 water, leaving behind, for the currents to carry away, the solid 

 matter which, as sea water, it held in solution. On the other 

 hand, numerous rivers discharge themselves into the Mediter- 

 ranean, some of which are filtered through soils and among 

 minerals which yield one kind of salts or soluble matter, another 

 river runs through a limestone or volcanic region of country, and 

 brings down in solution solid matter — it may be common salt, 

 sulphate or carbonate of line, magnesia, soda, potash, or iron — 

 cither or all may be in its waters. Still, the constituents of sea 

 water from the Mediterranean and of sea water from the Red Sea 

 are quite the same. But the waters of the Dead Sea have no 

 connection with those of the ocean ; thc}^ are cut off from its 

 channels of circulation, and are therefore quite different, as to 

 their components, from any arm, fiith, or gulf of the broad ocean. 

 Its inhabitants are also different from those of the high seas. 

 " The water which evaporates from the sea is nearly pure, 

 containing but very minute traces of salts. Falling as rain upon 

 the land, it washes the soil, percolates through the rocky layers, 

 and becomes charged with saline substances, which are borne 

 seaward by the returning currents. The ocean, therefore, is the 

 great depository of everything that water can dissolve and carry 

 down from the surface of the continents ; and, as there is no 

 channel for their escape, they of course consequently accumu- 

 late."* They would constantly accumulate, as this very shrewd 

 author remarks, were it not for the shells and insects of the sea. 

 and other agents mentioned. 



467. A general system of circulation required for tlie ocean. — How,, 

 therefore, shall we account for this sameness of compound, this 

 structure of coral (§ 4G5), this stability as to animal life in the sea, 

 but upon the supposition of a general system of circulation in the 

 ocean, by which, in process of time, water from one part is 

 conveyed to another part the most remote, and by which a 

 general interchange and commingling of the waters take place ? 

 In like manner, the constituents of the atmospliere, whether it 

 be analyzed at the equator or the poles, are the same. By cutting 

 oft and shutting up from the general channels of circulation any 

 portion of sea water, as in the Dead Sea, or of atmospheric air, as 

 in mines or wells, we can easily charge either with gases or 

 * Yoiunan'a Chemii-try. 



B 



