THE EARTH. 97 



halations from the earth, and deposited 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-watei 

 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 saltncss 

 at the beginning ; not only to prevent their corruption, but to enable 

 them to bear greater burthens. But their saltness does not prevent 

 their corruption ; for stagnant sea-water, like fresh, soon grows pu- 

 trid : and, as for their bearing greater burthens, fresh-water answers 

 all the purposes of navigation quite as well. The established opinion, 

 tnerefore, is that of Boyle,* who supposes, " That the sea's saltness 

 is supplied 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 wa- 

 ters, 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 likewise 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. 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 salt- 

 ness of its waters. " For if it be observed,"! says he, " what quantitv 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 contained 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 degree 

 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 

 modern curiosity ; and, I am induced to think, the inhabitants round 

 the Caspian Sea, will not be apt to undertake the inquiry. 



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

 much at the 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 communication 

 with the ocean, are found to be salt ; but some of them in less pro- 

 portion. 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 deposit 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 Aej 



Boyle, vol. iii. p. 221. t Phil - Trans, vol. v. p. 218. 



TOL. I. G 



