220 DOUGLAS WILSON JOHNSON 



Tertiary cycle, and erosion subsequently to the uplift at the close of 

 that cycle has been extensive. Sufficient time was not available for 

 the work in the field necessary to prove whether or not this test was 

 applicable, but it is not believed that satisfactory evidence of this 

 nature is obtainable. 



The winding character of the gorge. — In order to account for the 

 winding character of the Tennessee gorge, those who support the 

 theory of capture have been led to suppose a most complicated 

 hypothetical series of drainage rearrangements. This series involves: 

 the successive transference of divides from place to place along the 

 headwaters of three or four separate streams, by a roundabout course 

 some ten miles longer than that offered by the path of the stream 

 supposed to be first encountered by the diverting stream; the removal 

 of the massive sandstone cap throughout the courses of every one of 

 those streams even to their headwater areas preparatory to the cap- 

 ture; and the definite localization of the axis of a broad, gentle uplift 

 which is supposed to have determined the location of an assumed 

 divide between the supposed contending streams. There are two 

 difficulties in the way of accepting this explanation: It is impossible 

 to accept the assumption that the several streams were able to breach 

 the massive sandstone cap even to the divides between the streams, 

 whereas much larger and more powerful neighboring streams, with 

 all the advantage of post-Tertiary cutting, have scarcely begun to 

 accomplish that work in their lower courses. This will appear more 

 fully in a later paragraph. The proposed process of capture involves 

 so much that is purely hypothetical that one is led to seek a less com- 

 plicated explanation: 



The winding character of the gorge is, on the other hand, what 

 we should naturally expect if the meanders of the river are inherited 

 from a former baseleveling period when the river meandered broadly 

 over the site of the present ridge. Meanders which were developed 

 when the river flowed with sluggish course over the Cretaceous pene- 

 plain would necessarily intrench themselves with some modification 

 when the uplift occurred; and whatever the form of these meanders, 

 no special and complicated explanation would then be necessary in 

 order to account for each portion of the various curves. This more 

 simple explanation finds confirmation in the succeeding lines of evi- 

 dence. 



