THE EARTH. 



light to any but those whose pursuits are 

 lucrative, they need not be dwelt upon here. 

 While the merchant and the mariner are soli- 

 citous in describing currents and soundings, 

 the naturalist is employed in observing won- 

 ders, though not so beneficial, yet to him of a 

 much more important nature. The saltness 

 of the sea seems to be foremost. 



Whence the sea has derived that peculiar 

 bitterish saltness which we find in it, appears, 

 by Aristotle, to have exercised the curiosity 

 of naturalists in all ages. He supposed (and 

 mankind were for ages content with the solu- 

 tion) that the sun continually raised dry sa- 

 line exhalations from the earth, and deposit- 

 ed them upon the sea ; and hence, say his 

 followers, the waters of the sea are more salt 

 at top than at bottom. But, unfortunately for 

 this opinion, neither of the facts is true. Sea- 

 salt is not to be raised by the vapours of the 

 sun ; and sea-water is not salter at the top 

 than at the bottom. Father Bohours is of 

 opinion that the Creator gave the waters of 

 the ocean their saltness at the beginning ; 

 not only to prevent their corruption, but to 

 enable them to bear greater burthens. But 

 their saltness does not prevent their corrup- 

 tion ; for stagnant sea-writer, like fresh, soon 

 grows putrid: and, as for their bearing great- 

 er burthens, fresh waters answer all the pur- 

 poses of navigation quite as well. The esta- 

 blished opinion, therefore, is that of Boyle," 

 who supposes, " that the sea's saltness is sup- 

 plied not only from rocks or masses of salt at 

 the bottom of the sea, but also from the salt 

 which the rains and rivers, and other waters, 

 dissolve in their passage through many parts 

 of the earth, and at length carry with them 

 to the sea." But as there is a difference in 

 the taste of rock-salt found at land, and that 

 dissolved in the waters of the ocean, this may 

 be produced by the plenty of nitrous and bitu- 

 minous bodies that, with the salts, are like- 

 wise washed into that great receptacle. These 

 substances being thus once carried to the 

 sea, must for ever remain there ; for they do 

 not rise by evaporation, so as to be returned 

 back from whence they came. Nothing but 

 the fresh waters of the sea rise in vapours ; 

 and all the saltness remains behind. Hence 



Boyle, vol. iii. p. 221. 



it follows, that every year the sea must be- 

 come more and more salt ; and this specula- 

 tion Doctor Halley carries so far as to lay 

 down a method of finding out the age of the 

 world by the saltness of its waters. " For if 

 it be observed," 1 " says he, " what quantity of 

 salt is at present contained in a certain weight 

 of water, taken up from the Caspian Sea, for 

 example, and, after some centuries, what great- 

 er quantity of salt is contained in the sanif 

 weight of water taken from the same place ; 

 we may conclude, that in proportion as the 

 saltness has increased in a certain time, 

 so much must it have increased before that 

 time ; and we may thus, by the rule of pro- 

 portion, make an estimate of the whole time 

 wherein the water would acquire the degree 

 of saltness it should be then possessed of." 

 All this may be fine ; however, an experi- 

 ment, begun in this century, which is not to 

 be completed till some centuries hence, is 

 rather a little mortifying to modern curiosity : 

 and, I am induced to think, the inhabitants 

 round the Caspian Sea will not be apt to un- 

 dertake the inquiry. t 



This saltness is found to prevail in every 

 part of the ocean ; and as much at the sur- 

 lace as at the bottom. It is also found in all 

 those seas that communicate with the ocean; 

 but rather in a less degree. 



The great lakes, likewise, that have no 

 outlets nor communication with the ocean, 

 are found to be salt: but some of them in 

 less proportion. On the contrary, all those 

 lakes through which rivers run into the sea, 

 however extensive they be, are, notwithstand- 

 ing very fresh: for the rivers do not deposite 

 their salts in the bed of the lake, but carry 

 them, with their currents, intotheocean. Thus 

 the lakes Ontario and Erie,in North America, 

 although for magnitude they may be consi- 

 dered as inland seas, are, nevertheless, fresh- 

 water lakes ; and kept so by the river St. 

 Lawrence, which passes through them. But 

 those lakes that have no communication with 

 the sea, nor any rivers going out, although 

 they be less than the former, are, however, 

 always salt. Thus, that which goes by the 

 name of the Dead Sea, though very small, 

 when compared to those already mentioned, 



b Phil. Trans, vol. v. p. 218, 



