202 HUMAN FOSSIL OF NATCHEZ. CHAP. xi. 



shells, are produced, as before stated, p. 129, in all great 

 alluvial plains, where the river shifts its position, and where 

 marshes, ponds, and lakes are formed in its old deserted 

 channels. In this part of America, however, it may have 

 happened that some of these lakes were caused by partial 

 subsidences, such as were witnessed, during the earthquakes 

 of 1811-12, around New Madrid, in the valley of the 

 Mississippi. 



Owing to the destructible nature of the yellow loam, d e, 

 fig. 26, every streamlet flowing over the platform has 

 cut for itself, in its way to the Mississippi, a deep gully or 

 ravine ; and this erosion has of late years, especially since 1812, 

 proceeded with accelerated speed, ascribable in some degree 

 to the partial clearing of the native forest, but partly also to 

 the effects of the earthquake of 1811-12. By that con 

 vulsion the region around Natchez was rudely shaken and 

 much fissured. One of the narrow valleys near Natchez, due 

 to this fissuring, is now called the Mammoth Ravine. Though 

 no less than seven miles long, and in some parts sixty feet 

 deep, I was assured by a resident proprietor, Colonel Wiley, 

 that it had no existence before 1812. With its numerous 

 ramifications, it is said to have been entirely formed since 

 the earthquake at New Madrid. Before that event, Colonel 

 Wiley had ploughed some of the land exactly over a spot 

 now traversed by part of this water-course. 



I satisfied myself that the ravine had been considerably en 

 larged and lengthened a short time before my visit, and it 

 was then freshly undermined and undergoing constant waste. 

 From a clayey deposit immediately below the yellow loam, 

 bones of the Mastodon ohioticus, a species of megalonyx, 

 bones of the genera Equus, Bos, and others, some of extinct 

 and others presumed to be of living species, had been 

 detached, and had fallen to the base of the cliffs. Mingled 

 with the rest, the pelvic bone of a man., os innominatum, 



