CHAP. XXXIV.] OSCILLATION OF LEVEL. 261 



surface of what was once the river-plain at the period 

 of greatest depression, would remain fringing the val 

 ley sides as a terrace, apparently flat, but in reality 

 sloping down with the general inclination of the 

 valley. Everywhere this terrace would present cliffs 

 of gravel and sand facing the river. 



After these changes, the fundamental strata (Nos. 

 3,4, 5. %. 11. p. 262.) might be restored nearly to 

 their ancient positions; the freshwater beds (No. 2.) 

 having been raised, and having suffered great de 

 nudation. 



It is not improbable that the same series of move 

 ments gave rise to the accumulation and present 

 position of marine strata of comparatively modern 

 date, forming the lower terrace near Darien in 

 Georgia* which is indicated at 2*, in the annexed 

 section (fig. 11.). The reader will remember that the 

 remains of the megatherium, mastodon, elephant, 

 Harlanus, equus, and other extinct species of land 

 quadrupeds, are there associated with marine shells, 

 of species agreeing with those now inhabiting the 

 Atlantic. 



On the other hand, there are proofs in Texas of 

 the prevalence of the same succession of subterranean 

 movements far to the south-west, along the country 

 bordering the Gulf of Mexico : for on the Brazos 

 river there are beds of loam, or loess, examined by 

 Dr. Dickeson, and, when at New Orleans, I saw the 

 bones of extinct quadrupeds brought from that de 

 posit. Among them was the jaw-bone of a tapir, 



* See ante, vol. i. p. 346. 



