February 14, 1913] 



SCIENCE 



243 



very large volume left to represent any 

 earlier drainage. 



The entire argument for deep ice erosion 

 in the Finger Lake region is based on 

 physiographic features, hanging valleys 

 and "oversteepened" valley walls. The 

 writer believes that sufficient attention has 

 not been given to the effects of Prepleisto- 

 eene drainage in connection with the cli- 

 matic, topographic and diastrophie factors. 

 The high elevation of the northern part of 

 the continent in Tertiary time seems to be 

 a fact, and accompanied by warm climate. 

 If necessary to explain phenomena we may 

 assume effective vertical movements in our 

 region. The Tertiary was certainly a time 

 of vigorous drainage and remarkable val- 

 ley-cutting in northern lands. When the 

 fiord valleys were making in other lands 

 what was doing here? Undoubtedly our 

 rivers were also active, and the deep valleys 

 of central New York are one result. 



At the last Baltimore meeting of the so- 

 ciety the writer exhibited a series of maps 

 suggesting the drainage evolution in New 

 York.' The high "Hung-up" valleys with 

 northeast by southwest direction, and 

 mostly without present streams, seem to be 

 an inheritance from the primitive drain- 

 age on the new land surface. The drain- 

 age lines of the upper tributaries to the 

 Delaware and Susquehanna rivers preserve 

 their original direction. During some Pre- 

 pleistocene time the development of subse- 

 quent valleys along the strike of the thick 

 and weak Ontario strata resulted in a great 

 east and west valley, carrying a great trunk 

 stream, the hypothetical Ontarian River. 

 Into this valley was drawn from the south, 

 as obsequent streams, all the drainage of 

 western and central New York and the ad- 

 jacent territory of northern Pennsylvania. 

 The Susquehanna River turned northward 



'Geol. Soc. Am., Bull, Vol. 20, pp. 668-670, 

 1910. 



at Elmira and occupied the Seneca Valley, 

 which probably accounts for the excessive 

 depth of the valley, a drilling at Watkins 

 of 1,200 feet failing to reach rock. The 

 Genesee River is the one stream which fully 

 represents the Preglacial northward flow, 

 having held to its northward direction 

 clear across the state in spite of the tend^ 

 ency of glaeiation to force it into south- 

 ward flow. All the other drainage of south- 

 central New York was forced to southward 

 escape, mostly in tribute to the Susque- 

 hanna and through the new rock gorge at 

 Towanda, Pa. A late and probably rapid 

 land uplift, rejuvenating the obsequent 

 drainage, will probably be found to satis- 

 factorily account for the great depth and 

 other anomalous features that have been 

 used as arguments for deep glacial erosion 

 in New York. Interglacial drainage may 

 also be important in this work. 



It will now be understood that when the 

 earliest ice sheet invaded New York it 

 found a topography unlike the present, a 

 remarkable series of parallel, deep, opeil) 

 north-sloping valleys that headed south- 

 ward, the larger ones in Pennsylvania. 

 The present divides in the valleys are due 

 to the moraine fillings left by the ice. The 

 deep canyon-like valleys were occupied by 

 the glacier and some abrasion and smooth- 

 ing of the walls was inevitable. But it 

 should not be forgotten that the ice tongues 

 in these valleys were not mountain glaciers, 

 but merely lobations of a drift-burdened 

 margin of an ice sheet moving on an up- 

 slope. Conceding some erosive power to 

 the ice tongues in the valley, then instead 

 of deepening the valleys and oversteepen- 

 ing the walls and so producing the present 

 convex cross-profiles they should have cut 

 the walls and widened the valleys and pro- 

 duced concave profiles. In the work of 

 stream glaciers convexity of valley slope is 

 succeeded by concavity. In final word, to 



