236 R. S. TARR — DRAINAGE FEATURES OF CENTRAL NEW YORK 



valley broadens both ways from a narrow central portion, in which there 

 is a low rock divide near the present divide, which is in drift. This " hol- 

 low " is therefore a double valley, with both a sloping bottom and flaring 

 walls on each side of the divide. Its form is gorge-like, its walls re- 

 markably straight and smooth, and its tributaries confined to small 

 streams, which head on the very edge of the " hollow." 



Such steep, smooth, straight valley walls, though nowhere on the Wat- 

 kins Glen quadrangle as well developed as in Texas hollow, are, never- 

 theless, a common type of topography in this region (see plates 37 and 

 38). They are found, for example, south of both Watkins and Ithaca ; 

 in the Cayuta valley ; near Elmira ; in the valley southwest of Mecklen- 

 burg ; and in many other places. Such valley walls are most perfectly 

 developed in the neighborhood of lowered divides, and they occur in 

 both north-south and east-west valleys. 



Divides of smaller streams. — Many of the smaller headwaters are located 

 in broad, cirque-like, upland valleys, whose divide crest commonly 

 reaches elevations of from 1,500 to 1,800 feet. These upland valleys, 

 which are decidedly mature in form, frequently have gorges cut in their 

 bottoms, and in some cases are breached by gorges. The best and most 

 typical instance of this so far observed is on the very edge of the Wat- 

 kins sheet, almost due west of Watkins. A very perfect cirque-like 

 valley faces eastward, and the smooth, regular divide is cut completely 

 across by the gorge of a west-flowing stream. 



From this condition there is every stage to such cases of complete 

 obliteration of divides as those described above. Southwest of Van 

 Etten, for instance, the divide between Baker and Wyncoop creeks (see 

 plate 42, figure 2), is a low, flat-bottomed valley, bounded by smooth, 

 straight-sided, precipitous walls. Just south of Breesport, at the head 

 of Baldwin Creek valley, the divide is so low that if the gravel plain that 

 was built at the closing stages of the ice occupation could be removed 

 Newtown creek could be easily diverted across it. These instances may 

 serve as types which could be added to if it were necessary ; and it should 

 be noted that both in the large and small valleys there are instances of 

 lowered divides extending in all directions. 



Present stream courses. — The facts stated above prove conclusively that 

 there has been a widespread condition of divide lowering in the region 

 under consideration. Exactly the extent to which this lowering has 

 been carried in the major valleys is not certain because of the drift fill- 

 ing ; but in some of the smaller valleys the divide lowering has not gone 

 so far that the glacial deposits have obliterated the rock divide. 



Whatever the cause for the lowering of the divides, the present stream 



