TERTIARY HISTORY OF THE TENNESSEE RIVER 219 



in the direction of D to some point C, by what is termed the "inverted 

 stream," whose profile is B'C. It is possible that the profile CD' 

 may remain practically coincident with CD. In the interstream 

 areas remnants of the old valley floor between A and C not yet destroyed 

 by erosion will show surfaces which coincide with the prolongation 

 of the line CD toward A . 



On the other hand, if C represents a divide which has been long 

 maintained, no large stream having flowed from A to D, then the 



Fig. 7 



profiles will be as represented in Fig. 8 : streams flowing from A and C 

 toward B to meet and find an exit from the valley developing the 

 profiles AB and BC, while the stream flowing from C toward D 

 developed the profile CD. Now, if the streams intrench themselves, 

 remnants of the old valley floor in the interstream areas between A 

 and C will show surfaces which do not coincide with the prolongation 

 of the line CD. It may thus be possible, by a study of the inter- 



Fig. 8 



stream spaces, to determine whether the present profile of the streams, 

 A'B'C'D', which is much the same in either case, is developed as a 

 result of capture (Fig. 7), or merely represents the intrenching of 

 streams which have long maintained their present general relations 

 (Fig. 8). 



The limited application of this test is evident. It would not apply 

 to young streams with narrow valleys. It is equally obvious that if 

 the streams had reduced their valleys nearly to baselevel, so that all 

 slopes were very slight, and recent erosion had greatly dissected the 

 former valley floors, the detection of the desired evidence might be 

 impossible. In the case of the Tennessee drainage the streams 

 had reduced their valley floors nearly to baselevel at the close of the 



