NATURAL HISTORY. 51 



poration when even doubled or trebled, in order to 

 estimate the water which falls back into the sea, and 

 which is not conveyed over the earth. Mr Halley has 

 demonstrated that the vapours which rise above the 

 sea, and which the winds convey over the whole earth 

 are sufficient to form all the rivers, and to contain all 

 the waters which are on the surface of the earth. 



In the old continent there are about 430 rivers, 

 which fall directly into the ocean, or into the Mediter- 

 ranean and Black Seas, and in the new continent, 

 scarcely 180 rivers- are known, which fall directly into 

 the sea. In this number, however, I have included none 

 hut such as are as large as the river Somme in Picardy. 

 All these rivers carry to the sea a great quantity of 

 mineral and saline parts, which they have washed 

 from the different soils through which they have passed. 

 The particles of salt which are known to be easily dis- 

 solved, are conveyed to the sea by the water. Some 

 naturalist?, and among the rest Halley, have pretended 

 that the saltness of the sea proceeded only from the 

 salts of the earth, which the rivers transport thither. 

 Others assert, that the saltness of the sea is as ancient 

 as the sea itself, and that this salt was created only 

 that it might not corrupt, but it may be well supposed 

 that the sea is preserved from corruption by the agita- 

 tions of the wind, and the flux and reflux, as much as 

 by the salt it contains ; for when it is kept in a bar- 

 rel, it corrupts in a few days ; And Boyle relates that 

 a mariner becalmed for 13 days, found at the end of 

 that time the sea so infected, that if the calm had not 

 ceased, the greatest part of las people on board would 

 have perished. The water of the sea is also .mixed 

 with a bituminous oil, which gives it a disagreeable 

 taste, and renders it very unhealthy. The quantity 



