33'^ 



ISAIAH BOWMAN 



and an excellent pocket specimen, as it were, for classes in field 

 geography. Since the discovery of this example of stream-capture, a 

 study of the map reveals evidences of other cases near Ypsilanti which 

 will be studied in the field during the spring and summer. 



Relation to examples previously discussed. — The seizure of drain- 

 age areas of weak streams by more powerful adjacent streams forms 

 an interesting phase in physiography. Broadly speaking, two 

 forms of stream-capture may be recognized. The one takes place 

 gradually through the headward growing of streams flowing down 

 the steep inface of a cuesta, the captured stream originally flowing 

 down the gentler outface. Gilbert describes such cases in his The 

 Geology of the Henry Mountains, and Heim long ago pointed out the 

 capture of the Inn by the steep-sloping Maira. To this class belong 

 also cases later described by Professor Davis: the capture of the upper 

 Schmiecha by the Eilach in the Swabian Alps, piratical Deer Run in 

 eastern Pennsylvania, and a number of cases along the Blue Ridge of 

 Tennessee. 



Kaaterskill sheet. New York, of the U. S. Geological Survey, 

 topographic sheets, shows Plaaterskill Creek undercutting the 

 drainage areas of a southern tributary of Scoharie Creek; while a 

 northern tributary is being undercut by the Kaaterskill. Both the 

 Plaaterskill and Kaaterskill run directly into the Hudson, making a 

 descent of about 900 feet in the first few miles of their course. Scoharie 

 Creek drains northward into the Mohawk, and so finally into the 

 Hudson, and must descend but 900 feet in at least fifty miles. It is 

 therefore losing territory to the more vigorous streams gnawing into 

 the eastern border of the upland. 



The river systems of the Atlantic coast owe their present extension 

 to westward cutting. One by one the streams of the Appalachian 

 region have been diverted to the Atlantic, until but a single river 

 continues its original course to the Mississippi. This is the Kanawha, 

 wearing in canyon form the marks of its long struggle against the 

 diverting tendency. 



The second form of capture is accomplished by the sidfeways 

 swinging of a master-stream, which may thus eventually eat into the 

 side of a neighboring stream or behead one of its own tributaries. It 

 may have been in this manner that the Red River came to enter the 



