24 MODERN HAYINES. [CHAP. XXI. 



180 feet, was the result. (See fig. 7. p. 25.) The high 

 road has been several times turned to avoid this 

 cavity, the enlargement of which is still proceeding, 

 and the old line of road may be seen to have held 

 its course directly over what is now the widest part 

 of the ravine. In the perpendicular walls of this 

 great chasm appear beds of clay and sand, red, white, 

 yellow, and green, produced by the decomposition In 

 situ of hornblendic gneiss, with layers and veins of 

 quartz, as before-mentioned, and of a rock consisting 

 of quartz and felspar, which remain entire to prove 

 that the whole mass was once crystalline. 



In another place I saw a bridge thrown over a 

 recently formed gulley, and here, as in Alabama, the 

 new system of valleys and of drainage, attendant on 

 the clearing away of the woods, is a source of serious 

 inconvenience and loss. 



I infer, from the rapidity of the denudation caused 

 here by running water after the clearing or re 

 moval of wood, that this country has been always 

 covered with a dense forest, from the remote time 

 when it first emerged from the sea. However long 

 may have been the period of upheaval required to 

 raise the marine tertiary strata to the height of more 

 than 600 feet, we may conclude that the surface has 

 been protected by more than a mere covering of 

 herbage from the effects of the sudden flowing off 



O O 



of tli e rain water. 



I know it may be contended that, when the granite 

 and gneiss first rose as islands out of the sea, they may 

 have consisted entirely of hard rock, which resisted 

 denudation, and therefore that we can only affirm 



