CHAP. XXXIV.] OF NATCHEZ AND OHIO. 257 



are the monuments of an ancient alluvial plain, of an 

 age long anterior to that through which the Mis- 

 Fig. 10. 



VALLEY OF THE MISSISSIPPI. 



C 



Louisiana. Missi. R- 



j ( Vicksburg. &quot;o 



2 &quot;~ 



3 Q 1 :i 4 



1. Alluvium. 2. Loess. 3. /. Eocene. 4. Cretaceous. 



sissippi now flows, which was inhabited by land and 

 freshwater mollusca agreeing with those now ex 

 isting, and by quadrupeds now for the most part 

 extinct. 



In my former (i Travels in North America,&quot; I de 

 scribed some ancient terraces of gravel, sand, and 

 loam, occurring everywhere in the valley of the 

 Ohio, and gave a section of them as they are seen at 

 Cincinnati.* I pointed out that the included fossil 

 shells demonstrate the fluviatile and modern origin of 

 the deposits, and suggested that their present position 

 could only be explained by supposing, first, a gra 

 dual sinking down of the land after the original exca 

 vation of the valley, during which period the gravel 

 and sand were thrown down, and then an upheaval 

 of the same valley, when the river cut deep channels 

 through the freshwater beds.f Certain swamp form 

 ations observable in the valleys of small tributaries 

 of the Ohio, such as those of Big Bone Lick, in 



* Travels in North America, fig. 9., vol. ii. p. 59. chap. xvii. 

 f The second terrace (c, fig. 9. ibid.) at Cincinnati, may 

 imply a second oscillation. 



