THE CENTRAL BASIN OF TENNESSEE. 103 



of them are remarkably crooked with a gentle fall, some of them hav- 

 ing not more than thi'ee or fonr inches to the mile, and in places only 

 a succession of pools united by gentle ripples. 



The Cuml)er]and River which drains more than Iialf of the Central 

 Basin has an average fall between Port Burnside and Nashville of 

 about eight inches to the mile, but this is due to what might be called 

 a succession of jumps of a foot and sometimes a foot and a half at the 

 various shoals and ri])ples which occur throughout the course of the 

 river and which, to a considerable extent, impede the navigation of 

 the stream. In reality the current for long stretchr s of the river is 

 almost altogether due to the impetus given by these ripi)les or steps. 



The area now covered by tlie Cientral Basin of the Tennessee was, 

 at the close of the sub-carboniferous period, occupied by a dome-like 

 structure, the apex of which was at least 1,500 feet higher than the 

 floor of the Basin as it now appears. This dome was probably sur- 

 rounded by smaller ones of the same description. A small dome of 

 this nature and exhibiting the structure of the larger one is to be 

 found in Stewart County. It is called by Professor SafFord " Wells 

 Creek Basin." On the principle or general law of erosion that the 

 highest point is always attacked first, the apex of tliis central dome 

 would be subjected to wear before the other portions of the region. 

 There is every probability also thac the harder beds lying upon the 

 surface would be fractured and cracked in various places. These 

 fractures would admit water and form an underground drainage 

 which eroded the underlying soft beds forming the vast series of 

 caverns such as are found underlying the sub-carboniferous rocks of 

 Kentucky. The water falling upon the slopes of the dome would 

 form the drainage which was eroding the overlying hard rocks. In 

 course of time this erosion had so planed and denuded the top and 

 the underground streams having formed a series of caverns connected 

 with their channels that the Cumberland River, on passing through 

 the barrier of less eroded rocks, entered the region of the Basin and 

 found comparatively little resistance by the softer rocks where left 

 standing by the underground waters, luidermined the remaining upper 

 beds and eventually removed them. The river, having reached its 

 base level of erosion, its energies were expended in lateral erosion, 

 and the result is that the Cumberland has wandered from side to side 



