236 STUDIES OF NATL'RE. 



the ftreams, deflined to water the Earth, muft fre- 

 quently have deluged it. 



Nature employs ftill other means for fccuring 

 the courfe of rivers, and efpecially for protetfting 

 their difcharges into the Sea. The chief of thefe 

 are illands. Iflands prefent, to the rivers, chan- 

 nels of different diredions, that if the Winds, or 

 the Currents of the Ocean, fhould block up one 

 of their outlets, the waters might have a free paf- 

 fage through another. It may be remarked, that 

 flie has multiplied iflands at the mouths of rivers 

 the mofb expofed to this twofold inconveniency ; 

 fuch as, for example, at that of the Amazon, which 

 is for ever attacked by the Eaft wind, and fituated 

 on one of the mod prominent parts of America. 

 There they are fo many in number, and form with 

 each other channels of fuch different courfes, that 

 one outlet points North-eaft, and another South- 

 eaft, and from the firfl to the laft the diflance is 

 upward of a hundred leagues. 



Fluviatic illands are not formed, as has been 

 currently believed, of folid fubftances waflied 

 down by rivers, and aggregated : they are, on the 

 contrary, for the moft part, very much elevated 

 above the level of thefe rivers, and many of them 

 contain rivers and mountains of their own Such 



elevated 



