228 DOUGLAS WILSON JOHNSON 



gravels are so well preserved on the small remnants of the Tertiary 

 peneplain situated near the present river and subjected to extreme 

 erosion, they should show doubly well on the beautifully preserved 

 portions of the peneplain near the present divide south of Chat- 

 tanooga where post-Tertiary erosion has been at a minimum. On 

 the other hand, if the Tennessee River took its present westward 

 course before the close of the Cretaceous period, and has maintained 

 that course throughout all Tertiary and more recent time, we should 

 not expect to find any such development of the gravels in the valley 

 southward from Chattanooga. Indeed, even if in earlier Cretaceous 

 times the river may have held some course carrying it farther south- 

 ward in this region (as is possible, perhaps even probable, on the 

 basis of either theory), the most that we could expect to find in the 

 way of gravels would be occasional scattered pebbles having no 

 relation to the Tertiary peneplain, since the erosion of Tertiary 

 time must have swept away all but occasional traces of what may 

 have existed in a former period. 



North and south of the divide the valley was examined for a 

 distance of forty miles to ascertain the character of the stream dis- 

 section and to discover traces of the Tertiary gravels. About ioo 

 miles of road were traversed, peneplain remnants being visited and 

 beds of streams examined. In all this district not more than a few 

 dozen pebbles were noted, aside from the angular fragments of 

 chert, etc., evidently of local origin. These gravels occurred at 

 scattered intervals, usually only a few at a place, and in or near 

 the beds of streams draining high land areas. A longer and more 

 detailed search would, of course, show other scattered traces of these 

 gravels, but their extreme scarcity cannot be doubted. This re- 

 markable lack of the gravel seems irreconcilable with the theory 

 of capture, but is just what we should expect on the basis of the 

 alternative theory. 



On the divide between the Tennessee and Coosa- Alabama basins 

 the Tertiary peneplain developed in this broad valley east of the 

 ridge is very well preserved. As has been pointed out before, this 

 peneplain is not well developed across the entire breadth of the valley, 

 but where it has been so developed it remains very little dissected 

 by subsequent erosion. The conditions are here especially favor- 



