SALTNESS OF THE SEA. 17 



to twenty-nine. It is also stated that as the salt increases at a certain 

 depth, the water becomes less bitter. At the mouth of the great 

 rivers it is scarcely necessary to add that the water is always less 

 saline than on shores which receive no supplies of fresh water ; the 

 same remark applies to sea water in the vicinity of polar ice, the 

 melting of which is productive of much fresh water. A recent analysis 

 of the water of the Dead Sea by M. Eoux gives about two pounds of 

 salt to one gallon of water. No mineral water, if we except that of 

 the Salt Lake of Utah, is so largely impregnated with saline substances ; 

 the quantity of bromide of magnesia is 0'35 grammes to the litre. 

 The water of the Dead Sea is, according to these proportions, the 

 richest natural depository of bromide, which it might be made to 

 furnish abundantly. The waters of the great Lake of Utah and Lake 

 Ourmiah in Persia are both highly saline. In Lake Ourmiah, as in 

 the Dead Sea, the proportion of salt is six times greater than in the 

 ocean. Many of our fresh-water lakes were probably salt originally, 

 but have by degrees lost their saline properties by the mingling of 

 their waters with those of the rivers which traverse or flow into them. 

 Among the lakes which appear to have been divested of their saline 

 properties may be mentioned the great lakes of Canada and the Sea 

 of Baikal, in all of which seals and other marine animals are still 

 found, which have become acclimatized as the water gradually became 

 fresh. 



The saltness of sea water increases its density, and at the same 

 time its buoyancy, thus adapting it for bearing ships and other 

 burdens on its bosom ; moreover, to abbreviate slightly Dr. Maury's 

 remark, " the brine of the ocean is the ley of the earth." From it 

 the sea derives dynamical power, and its currents their main strength 

 It is the salt of the sea that imparts to its waters those curious 

 anomalies in the laws of freezing and of thermal dilatation, that assist 

 the rays of heat to penetrate its bosom ; the salts of the sea invest it 

 with adaptations which fresh water could not possess. In the latter 

 case, the maximum density would be thirty-nine degrees two seconds F. 

 instead of twenty-seven degrees two seconds F., when the dynamical 

 force of the sea would be insufficient to put the Gulf Stream in 

 motion. Nor could it regulate those climates we call marine. 



We have said that sea water contains nearly all the soluble sub- 



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