TERTIARY HISTORY OF THE TENNESSEE RIVER 225 



Fig. 9 



fully satisfy the objection urged, and does involve two other serious 

 difficulties. If we accept a theory of a channel across this divide 

 at the point north of Lafayette, we must account for the fact that 

 small branch streams all over this area have been able to develop 

 low, flat divides of remarkably uniform altitude, and having the 

 same elevation as the 

 channel in question. 

 And, since in nearby 

 areas elevations of 1,000 

 feet are represented by 

 Dr. Hayes as monad- 

 nocks rising above the 

 peneplain, we must either 



accept the idea of the narrow valley north of Lafayette referred to 

 in the preceding paragraph, or else assume a very restricted local 

 warping of more than 100 feet in four miles. It is also true that 

 no direct evidence of the existence of any channel across the divide 

 has been presented. For these and other reasons that will appear, 

 I am forced to agree with the earlier statement that "no channels 

 are cut in the Tertiary peneplain across the Coosa-Tennessee 

 divide." 



Insufficient inequality of levels between the two valleys. — In order 

 that one stream, 5 (Fig. 9), may divert another stream, A, from its 

 course, it is essential that the stream S occupy a level so much lower 

 than its neighbor A that even the uppermost headwater portions 

 of the branch O which effects the capture shall eventually be able 

 to work at a lower level than that of the stream to be captured. 

 That a small branch of the Sequatchie River, a stream which is 

 itself comparatively small, could work back through a high mountain 

 barrier along a course over 40 miles in length, and still have its 

 headwaters low enough to capture the large Appalachian River, 

 demands that the Sequatchie valley west of the ridge should have 

 been much lower than the Appalachian valley to the east. Several 

 conditions indicate that such a marked inequality of level did not 

 exist between the two valleys at the close of the Tertiary cycle. 



On theoretical grounds alone we should be led seriously to ques- 

 tion the possibility of such an advantage of position developing 



