DRA IN A GE MODIFICA TIONS 6/1 



dentl\- the result of the same cause. This is doubtless the uplift 

 already described by C. VV. Hayes and myself;' an uplift which 

 accelerated the northwestward flowing streams, but retarded 

 Clinch River by crossing that stream some distance below its 

 source. 



(^) River basins of Ke^itiicky. — The state of Kentucky, lying 

 almost entirely within the undisturbed region of the Mississippi 

 Valley, presents a fine field for the study of drainage forms. A 

 glance at the map of the state shows that even in that region of 

 nearl}' horizontal rocks the drainage is not well balanced, the 

 stream basins are not symmetrical, and the divides are apparently 

 migrating. Shaler recognized these peculiarities, but he was 

 unable to offer an adequate explanation. He writes as follows :^ 

 "It is not easy to account for this irregularity in the dis- 

 position of the streams away from the mountain regions. Away 

 from those disturbed regions there are only slight irregularities 

 in the rocks, which do not seem to have any power of determin- 

 ing the range of a river basin." He then suggests that their 

 peculiarities may be inherited from conditions in previous ages, 

 when the distribution of hard and soft rocks was very different 

 from that which prevails today. 



In the light of the present study, the arrangement of the 

 drainage lines of Kentucky is not peculiar ; in fact much of it is 

 most natural and what we would expect, if the surface slopes 

 from the interior toward the Ohio River. The divide on the 

 north side of Cumberland River is apparently encroaching on 

 that stream under an influence similar to that which permits Big 

 Sandy River to encroach upon Clinch River. This encroach- 

 ment is so pronounced that at one time it was proposed to divert 

 the waters of the upper Cumberland into Goose Creek, a branch 

 of the Kentucky River. The headwaters of Green River also 

 are crowding back toward the southeast against the Cumberland 

 basin and have now approached to within a ver}' few miles of 

 the main river. These divides must have migrated toward the 



' Geomorphology of the Southern Appalachians, Nat. Geog. Mag., Vol. VI, p. 94. 

 'Kentucky Geological Survey, Vol. Ill, New Series, p. 360. 



