666 MARIUS R. CAMPBELL 



characteristics which seem to mark such uplifts and separate 

 them from the general class. 



If a drainage basin, having a long circuitous outlet to the 

 sea, or one which is greatly retarded in its development by hard 

 rocks, maintains its balance against an opposing stream having 

 ready access to the sea, it is altogether probable that this bal- 

 ance has been maintained by an uplift which corresponded 

 originally with the divide between the basins. 



PART III. APPALACHIAN DRAINAGE. 



The preceding portion of this paper has been devoted to the 

 demonstration of the law of the migration of divides, and in 

 presenting the criteria by which such changes in the drainage 

 systems may be recognized. These criteria are divisible into 

 three classes, indicative of different degrees of change, as follows: 



Class I . — Barriers or obstructions in the channel of a large 

 stream with attendant features which are indicative of very recent 

 movement, — so recent indeed as to have no effect upon the 

 alignment of the stream or any of its branches. 



Class 2. — Complete rearrangement of the minor drainage 

 lines. This points to a pronounced warping at a time so remote 

 that all of the lesser streams have become adjusted to it by 

 changing their courses as previousl)- described. 



Class J. — Certain arrangement of the trunk streams, indicative 

 of crustal movements of pronounced character and of very 

 ancient date. 



It now remains to examine hastily some of the drainage 

 systems of the United States, to see if we can detect any of these 

 characteristics. In so doing, attention will be confined almost 

 exclusively to the region east of the Mississippi River, as being 

 the one with which the writer is most familiar ; and in this Appa- 

 lachian region we shall consider only that portion which is south 

 of the great terminal moraine, for in glaciated regions the prob- 

 lem of stream modifications is entirely too complex for present 

 consideration. 



