184 THE PHYSICAL GEOGRAPHY OF THP SEA. 



by rain or river water, can "be brought down into the Eed Sea. 

 Its salts come from the ocean, and the air takes up from it, in the 

 process of evaporation, fresh water, leaving behind, for the cur- 

 rents to carry away, the solid matter which, as sea water, it held 

 in solution. 



501. On the other hand, numerous rivers discharge themselves 

 into the Mediterranean, some of which are filtered through soils and 

 among minerals which yield one kind of salts or soluble matter, an- 

 other 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 lime, magnesia, soda, potash, or iron — 

 either 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 con- 

 nection with those of the ocean ; they are cut off from its channels 

 of circulation, and are therefore quite different, as to their compo- 

 nents, from any arm, frith, or gulf of the broad ocean. Its inhab- 

 itants are also different from those of the high seas. 



502. " The solid constituents of sea water amount to about 3 J 

 per cent, of its weight, or nearly half an ounce to the pound. Its 

 saltness may be considered as a necessary result of the present 

 order of things. Rivers which are constantly flowing into the 

 ocean contain salts, varying from ten to fifty, and even one hund- 

 red grains per gallon. They are chiefly common salt, sulphate and 

 carbonate of lime, magnesia,* soda, potash, and iron ; and these 

 are found to constitute the distinguishing characteristics of sea 

 water. 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 sea- 

 ward by the returning currents. The ocean, therefore, is the great 

 depository of every thing 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 accumulate, "f They 



* It is the chloride of magnesium which gives that damp, sticky feeling to the 

 clothes of sailors that arc washed or wetted with salt water, 

 t Youman's Chemistry. 



