257 



extent, is a well known fact. Yet, on the other hand, 

 there are many rivers of nearly an equal size and ex- 

 tent, where there are no deltas, nor even the appear- 

 ance of alluvial deposites. 



Indeed it is admitted by that indefatigable histo- 

 rian, Major Lien nelly that " all capital rivers do not 

 form deltas."* 



And further, Mr. R. observes, " However, the for- 

 mation of such deltas, even by rivers of the first magni- 

 tude, is by no means universal ; on the contrary, some 

 of them terminate in deep inlets, or estuaries, instead 

 of projecting forms : or, if the expression may be al- 

 lowed, they terminate negatively, instead of positively. 

 Of this class may be recorded the great rivers of the 

 Amazons, Plata, and the Oronoko; besides many 

 others, which bring down an equal quantity of matter 

 of alluvion, with the Nile, the Ganges, or any other 

 river that may form the most projecting delta."f 



Thus, finding that all great rivers do not, alike, pro- 

 duce, or exhibit deltas at their mouths ; we have rea- 

 son to believe that their formation is not the natural 

 result of the deposition of alluvion, brought down by 

 their currents, but rather of a combination of causes 

 or circumstances: these I consider of three different 

 kinds, viz : 



Istly. The alluvion of the river. 



2dly. That produced by the winds, and 



* Rennell's Herodotus, page 481. t Do. page 483. 



