CHAP. XIX ] SUCCESSION OF TERRACES. 257 



of the main land immediately adjoining, has an average height 

 of from ten to twenty feet, although there are a few places where 

 it reaches forty feet, above the sea. It extends twenty miles in 

 land, and consists of sand and clay of very modern formation, as 

 shown by the included marine shells, which are like those of 

 Skiddaway, before mentioned,^ all identical with living species. 

 This superficial deposit, although chiefly marine, contains, in some 

 parts, beds of fresh-water origin, in which the bones of extinct 

 mammalia occur. The whole group would be called by geolo 

 gists fluvio-marine, and is of small depth, resting immediately on 

 Eocene, or lower tertiary strata, as I ascertained by examining 

 the shells brought up from several wells. Going inland twenty 

 miles, we corne to the termination of this lower terrace, and as 

 cend abruptly to an upper platform, seventy feet above the lower 

 one, the strata composing which belong to the Eocene period. 

 This upper terrace also runs back about twenty miles to the ab 

 rupt termination of a third table-land, which is also about seventy 

 feet higher, and consists of Eocene strata, by the denudation of 

 which all these terraces arid escarpments (or ancient sea-cliffs) 

 have been formed. Bartram has, with his usual accuracy, al 

 luded to these steps, or succession of terraces, as an important 

 geographical feature of the country, each of them being marked 

 by its own botanical characters, the prevailing forest-trees, as well 

 as the smaller plants, being different in each. 



To return to the first platform, or lowest land, from ten to 

 forty feet above the level of the sea, it consists of a modern de 

 posit, which extends 400 miles northward to the Neuse in North 

 Carolina, and probably farther, in the same direction, along the 

 Atlantic border. How far it stretches southward, I am not in 

 formed. I conceive it to have been accumulated in a sea, into 

 which many rivers poured during a gradual subsidence of the 

 land, and that the strata, whether fresh-water or marine, formed 

 during the sinking of the bottom of the sea, have been since 

 brought up again to their present elevation. Throughout this 

 low, flat region, the remains of extinct quadrupeds are occasion 

 ally met with, and the deposit appears to be very analogous to 

 * Ante, p. 234. 



