18 THE OCRFAN WORLD. 
evaporation. The saltness of this interior sea is only half as intense 
as that of the ocean. 
The Sea of Azov and the Caspian Sea are still less salt than the 
Black Sea. oe 
The following table shows the relative composition of the water 
in these three interior seas :— 
Black Sea. | Sea of Azov. | Caspian Sea. 
In 100 Gallons of Water. Density Density Density 
1013. 1009. 1‘005. 
Chloride of sodium . . . | 14'0195 96583 36731 
Chloride of potassium . . a*18g2 0°1279 00761 
Chloride of magnesium . . 1°3045 08870 06324 
Sulphate of magnesia . . 1°4704 07642 1°2389 
Sulphate of lime . . . . 0'1047 0°2879 0°4903 
Bicarbonate of magnesia. . 0°2086 0°1286 0'0129 
Bicarbonate of lime . . . | 073646 0'0221 0°1705 
Bromide of magresium . . 0°0052 0'0035 traces 
17°6663 | 11°8795 6°2942 
In some lakes without any outlet, as the Dead Sea and the Lake 
of Ural, the degree of saltness is considerably augmented. Nume- 
rous experiments have proved that the water of the Dead Sea is six 
times salter than that of the ocean. MM. Boutron and O’Henry 
analysed, in April, 1850, after the rainy season, some water of the 
Dead Sea, taken at about two leagues from the mouth of the Jordan ; 
its density was then r-1o. 
The saltness of sea water makes it more fitted to float ships, 
because its density is increased by the salts which are dissolved in it. 
Besides this, these salts contribute to prevent the water becoming 
contaminated with decomposed organic matter. 
By the table representing the composition of the water of the 
ocean and that of the Mediterranean, we see that salts of lime and 
potassium, as well as iodine and silica, are only found in infinitely 
small quantities. Nevertheless, the lime and silica contained in the 
sea water are of very great importance ; for these quantities, which 
appear to us so small in the table of a chemical analysis, become 
enormous in the entire extent of the ocean. The marine plants take 
up the lime, the silex, the potassium, and the iodides which are dis- 
solved in the sea water, and these mineral substances enter into 
their textures. It is from the carbonate of lime and silex that the 
