258 The American Geologist. April, isoa 
the exception of the cases already instanced, the rivers seem to 
have held the courses which they had had during Cretaceous time; 
at least there is no evidence of change from those courses. The 
movement of elevation embraced so wide an area that it did not 
affect the minor arrangement of the stream courses. The streams 
of the Cretaceous C3'cle were revived. Elevation gave them greater 
velocity and erosive power and the}' at once commenced to cut 
their channels to base-level and then to widen them out at that 
level. 
2. Tertiary work in Tennessee and Kentuchy. The larger part 
of the topography of Tennessee and Kentucky was fashioned out 
from the Cretaceous base-level plateau during Tertiary time. 
The broad valley of the East Tennessee with an average elevation 
of 1,000 feet above sea level and cut a thousand or more feet be- 
low the surrounding plateau is a Tertiary valley. It is a direct 
southward continuation of the Kittatiuny valley of New Jersey 
and Pennsylvania which is of Tertiary date. In western Tennes- 
see the Tennessee river has excavated during Tertiar}' time a 
broad deep valley similar to its valle}' in eastern Tennessee but 
not as deep, for the altitude of the plateau is not so great as in 
eastern Tennessee. 
A better illustration of the extent of Tertiary erosion is found 
in the central part of Tennessee. From the central lowland of 
Tennessee the strata dip away in all directions at low angles. If 
the strata which have been removed were to be restored the form 
of the surface would be a wide flat dome with its greatest eleva- 
tion over the center of the region. The capping of Carboniferous 
rocks over this region ma}" originally have been of less thickness 
than over surrounding regions. Whether pre-Tertiary erosion 
suflflced to strip off this cover of Carboniferous and sub-Car- 
boniferous rocks and to expose the softer Silurian strata beneath 
is not known. In any event pre-Tertiary erosion must have con- 
siderably lessened its thickness and have made it easier for Ter- 
tiary erosion to complete its removal. The erosion of the present 
central lowland could not have been the work of Cretaceous time, 
for during Cretaceous time the base-level of the region was sev- 
eral hundred feet above the present surface. But after the ele- 
vation of the Cretaceous base-level and the establishing of a new 
base- level at a lower level, the streams soon cut through the 
thinned covering of Carboniferous and sub-Carboniferous rocks 
