2± Campbell — Changes in the Drainage of Virginia. 



flowed was west ; and that its drainage basin included the 

 present basin of Guest river as far east as Coeburn. Figure 2 

 shows the ancient drainage reconstructed in accordance with 

 the above facts. Powell river then had its source on the 

 plateau east of Coeburn ; it flowed along the present valley of 

 Tom creek to Coeburn where it turned due west, receiving 



the various tributaries as they flow to-day and joined the 

 present Powell river a mile west of Norton. Before the 

 change occurred, Clinch and Powell rivers were flowing at 

 about the same elevation, but this was probably very much 

 nearer sea level than the streams flow at present. In the con- 

 test between their headwaters, the Clinch was retarded by the 

 upturned edge of the Carboniferous conglomerate against 

 which the main stream and its tributaries could make but little 

 headway, while Powell river was not hindered by any obstruc- 

 tion. ITnder these conditions the divide between them had 

 migrated back cpuite close to Clinch river as shown in fig. "2. 

 Being thus adjusted to the surrounding conditions, the two 

 rivers would have remained in equilibrium unless their balance 

 was disturbed by an external cause. This cause must have 

 been isostatic movement since no other kind of movement is 

 known to have occurred in late geologic time. But was it an 

 epeirogenic or orogenic movement that caused the change? 

 A broad uplifting of the district could not have produced this 

 effect for the relative position of the two streams would have 

 remained unchanged, therefore it must have been caused by a 

 local or orogenic uplift. Our conclusion however need not be 

 based upon this negative evidence for the region abounds with 

 positive proof of the warping of the earth's crust. 



The upper portion of the Clinch valley presents the youth- 

 ful features of a recently revived stream. Its character was 

 first recognized by Willis in 1885 and later studied in detail by 

 the writer. The river flows in a narrow channel 300 to TOO 



