THE CHATTANOOGA CAMPAIGNS. 



149 



have weathered with comparative slowness, ami consequently the mass 

 stands out iu strong relief, extending nearly to the Atlantic and most 

 effectively separating the southern Atlantic seaboard from the interior. 

 So effective a barrier were they that communication from the coastal 

 plain with northern Georgia, Tennessee and Kentucky was either by 

 the passes in Virginia or around the southern end of the mountains by 

 way of Atlanta. Prior to LSSO there was no railroad across these 

 mountains south of Roanoke. 



Some of the intermontane valleys are fertile and support a consid- 

 erable population, but the general inaccessibility of the region is shown 

 by the life and customs of the people, which have scarcely changed 

 since revolutionary times. 



In the tilting and folding incident to the formation of the Appa- 

 lachian system, there was exposed a belt of limestones and shales extend- 



Outline Map of the Region included in the Chattanooga Campaigns. 



ing in a direction roughly parallel to the mountain axis. These rocks 

 are tilted and their upturned edges are easily eroded as compared with 

 those on either side. The result of this erosion is an irregular trough 

 from ten to seventy-five miles wide and over a thousand miles long. 

 It is known in general as the 'Great' or Appalachian valley, but has 

 various local names. In New Jersey it is known as the Kittatinny 

 valley; in Pennsylvania it is the Cumberland valley; in Virginia it 

 becomes the Shenandoah valley and in this region, the Tennessee val- 

 ley or the East Tennessee valley. 



The rocks are much inclined and their parallel edges of different 

 degrees of resistance are exposed to the process of denudation, the 

 results of which are long, narrow, parallel ridges running lengthwise 

 along the valley. For example, the famous Chickamauga Ridge is com- 

 posed of a compact resistant rock, known as Knox dolomite, which 

 stands above the valley floor because the neighboring strata are less 

 resistant to the levelling effects of denudation. The traveler going 



