TERTIARY HISTORY OF THE TENNESSEE RIVER 223 



a cavern or series of caverns twenty-five or thirty miles in length, 

 having a beautiful meandering course, developed under a massive 

 cap of hard rock which came down nearly or quite to the level of the 

 valley floors. As Dr. Hayes has pointed out to me, such under- 

 ground channels would in this case run counter to the trend of geo- 

 logical structures in the region, whereas it is generally true that 

 caverns are developed parallel with such structures. The impossi- 

 bility of accepting this theory is further evident from the considera- 

 tion of points to follow. We are therefore forced to the conclusion 

 that the present breach through Walden Ridge was made by the 

 Tennessee itself, it having maintained its present course from a 

 former baseleveling period. 



Character 0} the divide south 0} Chattanooga. — The Tertiary pene- 

 plain on the present divide between the Coosa- Alabama and Tennes- 

 see basins, south of Chattanooga, is less than 1,000 feet above sea- 

 level. Those elevations rising to or above the 1,000-foot contour 

 are to be regarded as monadnocks which projected above the pene- 

 plain at the close of the Tertiary baseleveling period. Care was 

 taken to verify this statement in the field, in order not only to guard 

 against errors arising from incorrect maps, but particularly to elimi- 

 nate the effect of possible warping of the peneplain so much as to 

 bring it up to the 1,000-foot level. It was thus found that for a num- 

 ber of miles north and south of the divide those elevations contoured 

 as 1,000 feet or over, as well as a number of elevations not so repre- 

 sented on the map, rose distinctly above the peneplain level, and 

 that the above statement as to the altitude of the peneplain is correct. 



Now, if we take the Ringgold topographic sheet and color the 

 areas remaining unreduced at the close of the Tertiary cycle, it brings 

 out very clearly one serious objection to the proposed theory of cap- 

 ture. It will be seen that numerous remnants, some of them over 200 

 feet in height and of considerable areal extent, were left unreduced 

 on the present divide between the Tennessee and Coosa basins. The 

 supposed former southward course of the Appalachian across this 

 divide must have led between these remnants, because the capture 

 is represented as taking place at the close of the Tertiary. In order 

 to accept the theory of capture, then, we must conceive that a great 

 river, flowing over soft, valley-making rocks, still found itself at the 



