Drainage Conditions. 105 
resulting from a long period of subaeial rock decay. The divides 
were low, slopes gentle, and’ the drainage systems delicately 
adjusted among themselves. 
2.—TERTIARY CYCLE. 
The first cycle was brought to a close and the second cycle 
inaugurated by an uplift of the province. As explained in Part 
I, the maximum uplift was along certain axial lines which pro- 
duced a warping of the previously formed peneplain. The first 
effect of elevation was to revive the streams, so that they began 
active erosion of their channels. If the uplift had been uniform 
over the province the streams would simply have persisted in 
their old courses, but the warping gave some streams a decided 
advantage over others and the process of adjustment to new 
conditions produced some decided changes in the drainage. 
Owing to the delicate interadjustment which the streams had 
reached during the preceding long period of baseleveling, they 
were peculiarly susceptible to change, and the first slight warp- 
_ing, after the baseleveling, was productive of greater changes than 
that which occurred later. 
Effects of Uplift on the Axis O P.—The first decided movement at 
the beginning of this second cycle appears to have taken place 
along the axis O P, shown on plate 5. The effect which it pro- 
duced upon the drainage had so direct a bearing on the subse- 
quent diversion of the Appalachian river to the present course 
of the Tennessee that a somewhat detailed account of its effects 
will be given. 
It must be borne in mind that at the beginning of this cycle 
the most of the Appalachian valley was occupied by southward 
flowing streams, which discharged their waters directly into the 
Cretaceous sea; that the Sand mountain syncline south of the 
Tennessee gorge was occupied by a consequent stream also flow- 
ing southwestward to the Cretaceous sea, and that the Sequatchie 
anticline was held by a subsequent stream flowing, in its lower 
course, northwestward to the Mississippi embayment. The 
Cumberland river was at the same time a vigorous stream, prob- 
ably flowing nearly due westward along the present Kentucky- 
Tennessee line to the upper end of the Mississippi embayment. 
The plateau region was almost completely reduced to baselevel 
and the streams nicely balanced against each other. Under such 
conditions the slight uplift occurring along the line O P checked 
