292 LECTURE X. 



land shells before-mentioned are founds at different depths iia 

 the loam, the remains of the mastodon ; and clay immediately 

 under the loam, and above all the sand and gravel entire 

 skeletons of the Megalonyx, associated with the bones of the 

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

 if not all, extinct species. This great loamy formation, with 

 terrestrial and freshwater shells, extends horizontally for about 

 twelve miles inland or eastward from the river, forming a plat- 

 form about two hundred feet above, the great plain of the 

 Mississippi. In consequence, however, of the incoherent and 

 destructible nature of the sandy clay, every streamlet flowing 

 over what must originally have been a level table land, has cut 

 out for itself, on its way to the Mississippi, a deep gully or 

 ravine. 



" This excavating process has, of late years, proceeded with 

 accelerated speed, specially in the course of the last thirty or 

 thirty-five years. Some attribute the increased erosive action 

 to the partial clearings of the native forest, a cause, of which 

 the power has been remarkably displayed, as before stated, 

 within the last twenty years in Georgia. Others refer the change 

 mainly to the effects of the great earthquake of New Madrid, 

 in 1811-12, by which this region was much fissured, ponds 

 being dried up and many land-slips caused. 



''In company with Dr. Dickeson and Colonel Wailes I visited 

 a narrow valley, hollowed out through the shelly loam, recently 

 named " the mammoth ravine," from the fossils found there. 

 Colonel Wiley, a proprietor of that part of the State of Missis- 

 sippi, who knew the country well before the year 1812, assured 

 me that this ravine, although now seven miles long, and in 

 parts sixty feet deep, with its numerous ramifications, has been 

 entii'ely formed since the earthquake. He himself had ploughed 

 some of the land exactly over one spot which the gully now 

 traverses. 



" A considerable sensation was recently caused in the public 

 mind, both in America and Europe, by the announcement of 

 the discovery of a fossil human bone, so associated with the 

 remains of extinct quadrupeds in " the mammoth ravine" as 

 to prove that man must have co-existed with the Megalonyx 



