56 Professor Guyot on the Physical Geography of 



upon the very border of the Atlantic plain. The reason is that the 

 terrace which forms the base of the chains, and the slope of which 

 usually determines the general direction of the water courses, attains 

 here its greatest elevation, and descends gradually towards the north- 

 west. The base of the interior chain which runs alongside the Great 

 Valley is thus depressed to a lower level, and though the chain itself 

 has an absolute elevation greater than that of the Blue Ridge, the rivers 

 which descend from the summits of this last, flow to the northwest 

 towards the great central valley which they only reach, in southern 

 Virginia and North Carolina, by first passing across the high chain of 

 the Unaka and Smoky mountains through gaps of 3000 or 4000 feet 

 in depth. 



This southern division thus presents from southeast to northwest three 

 regions very distinct. 



The first is the high mountainous region comprised between the Blue 

 Ridge and the great chain of the Iron, Smoky, and Unaka mountains 

 which separate North Carolina from Tennessee. It commences at the 

 bifurcation of the two chains in Virginia, where it forms, at first, a valley 

 of only ten to fifteen miles in breadth, in the southern part of which flows 

 New River ; it then enlarges and extends across North Carolina and into 

 Georgia, in length more than 180 miles, varying in breadth from twenty 

 to fifty miles. The eastern chain, or Blue Ridge, the principal water- 

 shed, is composed of many fragments scarcely connected into a continu- 

 ous and regular chain. Its direction frequently changes and forms many 

 large curves. Its height is equally irregular. Some groups elevated 

 from 5000 feet and more, are separated by long intervals of depression 

 in which are found gaps whose height is 2200 to STOO feet, often but little 

 above the height of the interior valleys themselves with which they are 

 connected. The interior, or western chain, is much more continuous, 

 more elevated, more regular in its direction and height, and increases 

 very uniformly from 5000 to nearly 6700 feet. 



The area comprised between these two main chains, from the sources 

 of the New River and the "Watauga, in the vicinity of the Grandfather 

 Mountain, to the southern extremity of the system, is divided by trans- 

 verse chains into many basins, at the bottom of each one of which runs 

 one of those mountain tributaries of the Tennessee, which by the abund- 

 ance of their waters merit the name of the true sources of that noble river. 



Between the basin of the "Watauga and that of the Nolechucky rises 

 the lofty chain of the Roan and Big Yellow mountains. The northwest 

 branch of the Black mountain and its continuation as far as the Bald 

 mountain separate the basin of the Nolechucky from that of the French 

 Broad river. Between the latter and the Big Pigeon river stretches the 

 long chain of the Pisgah and the New Found mountains. Further to 

 the south the elevated chain of the Great Balsam mountains separates 

 the basins of the Big Pigeon and the Tuckasegec ; next comes the chain 

 of the Co wee mountains between the latter river and the Little Tennes- 

 see. Finally the double chain of the Nantihala and Valley River 

 mountains separates the two great basins of the Little Tennessee and 



