CHAP. XXXI.] OF NATCHEZ. : 195 



The resemblance of this loam to that fluviatile 

 silt of the valley of the Rhine, between Cologne and 

 Basle, which is generally called &quot; loess&quot; and &quot; lehm&quot; 

 in Alsace, is most perfect. In both countries the 

 genera of shells are the same, and as, in the ancient 

 alluvium of the Rhine, the loam sometimes passes 

 into a lacustrine deposit containing shells of the 

 genera Lymnea, Planorbis, and Cyclas, so I found 

 at &quot;Washington, about seven miles inland, or east 

 ward from Natchez, a similar passage of the Ame 

 rican loam into a deposit evidently formed in a pond 

 or lake. It consisted of marl containing shells of 

 Lymnea., Planorbis, Pdludina, Physa, and Cyclas, 

 specifically agreeing with testacea now inhabiting 

 the United States. With the land-shells before 

 mentioned are found, at different depths in the 

 loam, the remains of the mastodon ; and in clay, im 

 mediately under the loam, and above the sand and 

 gravel, entire skeletons have been met with of the 

 megalonyx, associated with the bones of the horse, 

 bear, stag, ox, and other quadrupeds, for the most 

 part, if not all, of extinct species. This great loamy 

 formation, with terrestrial and fresh-water shells, 

 extends horizontally for about twelve miles inland, 

 or eastward from the river, forming a platform about 

 200 feet high above the great plain of the Mississippi. 

 In consequence, however, of the incoherent and de 

 structible nature of the sandy clay, every streamlet 

 flowing over what must originally have been a level 

 table -land, has cut out for itself, in its way to the 

 Mississippi, a deep gully or ravine. This excavating 

 process has, of late years, proceeded with accelerated 



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