SALTNESS OF THE SEA, 17 
The water of the Mediterranean contains more salts than that of 
the ocean. 
The following are, according to M. Usiglio—who was one of a 
commiission sent to examine the different kinds of salt water in the 
south of France—the component parts of one hundred gallons of 
Mediterranean water :— 
Ibs, 
Chloride of sodium. : -  29°524. 
Chloride of potassium 0°405 
Chloride of magnesium . . +  3°219 
Sulphate of magnesia. ~ 2477 
Chloride of calcium ; 6080 
Sulphate of lime . - 1'557 
Carbonate of lime - . O1I4 
Bromide of sodium : - «  0'356 
Protoxide of iron . oe ee 07003 
43°735 
We conclude, from the quantity of sea salt contained in the 
water of the ocean, that if it were spread over the surface of the 
globe, it would form a layer of more than thirty feet in height. 
The salt contained in sea water gives it a greater density than 
fresh water; its average specific weight is 1027. The density of 
the water of the Mediterranean is, according to M. Usiglio, 1025 
when at the temperature of seventy degrees. But the saltness of 
the sea varies very much under the influence of a great many 
local circumstances, among which we must count principally cur- 
rents, winds favourable to evaporation, rivers coming from the 
continents, &c. 
It has been remarked that the sea is less salt towards the poles 
than at the equator ; that the saltness increases, in general, with the 
distance from land, and the depth of the water; that the interior 
seas, such as the Baltic, the Black Sea, the White Sea, the Sea of 
Marmora, and the Yellow Sea, are less salt than the ocean. The 
Mediterranean is an exception to this last rule; it is, as we have 
seen, salter than the ocean. This difference is explained by the fact 
that the quantity of fresh water brought into it by rivers is less than 
that lost by evaporation. The Mediterranean must therefore grow 
salter with time, unless its water is discharged into the ocean by a 
counter current, which would run under the current coming from the 
Atlantic by the Straits of Gibraltar. ; 
The Black Sea, on the contrary, the water of which has a density 
of only 1'013, receives from rivers more fresh water than it loses by 
Cc 
