114 Hayes and Campbell—Appalachian Geomorphology. 
Scottshoro when that was being cut, and the stream which flowed 
in that valley was probably smaller than the present Tennessee ; 
therefore, if under the same conditions a smaller stream than 
the present Tennessee could cut so broad a valley as it did in 
northern Alabama during the Tertiary cycle, the conclusion 
seems inevitable that the present gorge through Walden plateau 
has been occupied a very much shorter time, and hence the 
Appalachian drainage was not diverted to its present westward 
course till after a part or the whole of the Tertiary cycle. The 
explanation of the manner in which the writers believe the 
present winding course of the Tennessee tarough the plateau 
was acquired will be given in describing the process by which 
the diversion was accomplished. 
Conditions immediately preceding the Diversion—During the 
rapid elevation which inaugurated the Tertiary cycle and the 
much slower uplift which occurred near the close of the base- 
leveling period, the land area was enlarged by the addition of 
successive narrow belts of newly emerged sediments. In most 
cases the streams pushed their way across these belts by the 
shortest line to tidewater. The stream draining the Sequatchie 
anticline flowed westward through the plateau of northern Ala- 
bama by the broad valley already described; from the mouth 
of Flint river its course coincided with that of the present Ten- 
nessee to the Mississippi ine. From this point it flowed south- 
westward to the Mississippi embayment very nearly in the pres- 
ent position of Black river, crossing the Cretaceous sediments as 
they were exposed at the close of the Cretaceous cycle and the 
successive belts of Tertiary sediments as they slowly emerged 
during the latter part of the Tertiary cycle. 
The Tertiary cycle was marked near its close by a depression 
which effectually stopped the baseleveling process. This de- 
pression was not uniform, but lke the preceding elevation was 
accompanied. by warping of the surface. As indicated by the 
contemporaneous sedimentation, the depression was very slight 
at the present Gulf coast, 25 feet more or less at Mobile, increas- 
. ing northward to 650 feet or more on the Memphis-Charleston 
axis (A B, plate 6). Northward from this axis the depression 
decreased, passing into a pronounced uplift in the northern por- 
tion of the province. In other words, the southern portion of 
the province was tilted northward, decreasiny its seaward gra- 
dient, while a portion at least of the interior was tilted south- 
