Ififi HISTORY or 



waters of the sea rise in vapours ; and all the saltness retnaih? 

 behind. From hence it follows, that every year the sea must 

 become more and more salt ; and this speculation Dr 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," 

 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 greater quantity of salt is con- 

 tained in the same 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 proportion make an esti- 

 mate of the whole time wherein the water would acquire the de- 

 gree of saltness it should be then possessed of.'" All this may 

 be fine : however, an experiment, begun in this century, which 

 is not to be completed till some centuries hence, is rather a 

 little mortifying to modem curiosity ; and I am induced to think, 

 the inhabitants round the Caspian Sea will not be apt to under- 

 take the inquiry. 



This saltness is found to prevail in every part of the ocean ; 

 and as much at %he surface 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 communi- 

 cation 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, 

 notwithstanding, very fresh : for the rivers do not deposite their 

 salts in the bed of the lake, but carry them with their currents 

 into the ocean. Thus the lakes Ontario and Erie, in North 

 America, although for magnitude they may be considered as in- 

 IrMid seas, are nevertheless fresh-water lakes ; and kej)t 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 mention- 

 ed, is so exceedingly salt, that its waters seem scarcely capable 



1 Pliii. Trans, vol. v. p. 2ia 



