of the Northern Catskill Mountains. 141 



Hudson on the east and the Mohawk on the north, each of 

 which marks in a general way the trend, though probably not 

 the location, of the boundaries of the old land on the east and 

 north. The escarpments are accordingly the infaces of cuestas,* 

 the one set facing northward to the Adirondack Old Land ; 

 the other eastward to that beyond the Hudson. 



The splitting of the northern part of the Catskill escarpment 

 is due, presumably, to original differences in rock resistance 

 resulting, no doubt, from original differences in the constitu- 

 tion of the marginal portions of the great Catskill Delta, f The 

 weakening, and final dying out of the Catskill escarpments to 

 the west, particularly of the northern branch, is doubtless to 

 be explained in the same way— the rocks responsible for them 

 becoming finer, and less resistant farther out from the source 

 of supply, and consequently less able to maintain the escarp- 

 ments. 



Drainage. 



The drainage of the region accords closely with its structure. 

 In their broader relations the subsequent Hudson and Mohawk 

 lowlands separating the region from its old-land are strictly in 

 accord with the structural features. 



Of the streams draining the plateau the Susquehanna and 

 the Delaware on the west flow in consequent courses down the 

 dip toward the axis of the Paleozoic bay in which the rocks of 

 the plateau accumulated. Esopus Creek — evidently obsequent 

 — drains eastward directly into the Hudson ; whereas Schoharie 

 Creek — in its extreme upper course consequent, flowing down 

 the dip of the rocks ; in its middle course subsequent, follow- 

 ing the base of the Central Escarpment ; and in its lower 

 course obsequent — flows northward into the Mohawk. Cats- 

 kill Creek, in a subsequent valley, flows southeastward parallel 

 to the base of the Catskill Escarpment. Fox Creek and Cobles- 

 kill Creeks, both subsequent streams, follow the base of the 

 Hamilton Escarpment, while finally Bozen Kill parallels the 

 base of the Helderberg Scarp. 



The courses of all these, except possibly Esopus Creek, seem 

 to accord perfectly with the structure. Why this obsequent 

 stream should have been able to gnaw so far back into the 

 escarpment while those at the headwaters of Schoharie Creek 

 worked back only a short distance is puzzling. Again it may 

 be that the reason lies in the structure. The pattern of 

 Esopus Creek within the mountains is dendritic and perfectly 

 symmetrical. In this respect it differs radically from that of 



* Grabau, A. W., loc. cit. 



f Barrell, J., this Journal (4), xxxvi, 429-472, 1913; xxvii, 87-109, 225- 

 253, 1914. 



