60 H. L. FAIRCHILD — ICE EROSION THEORY A FALLACY 



the valley walls. This is inconsistent with the idea of erosion. The 

 only explanation seems to he that the ice contained little drift in front 

 of the drumlin belt zone of deposition, or that the valley ice was inac- 

 tive and melted back without long pause. It is not thought possible 

 that there could have been any serious erosion by valley lobes, saying 

 nothing of " hundreds of feet " of cutting, without leaving conspicuous 

 piles of debris, even in the presence of the glacial waters. 



Small volume of the valley-heads moraine. — The total volume of 

 the valley-heads moraine, after making liberal allowance for the valley 

 train drift south of that moraine and the fine material carried to the sea, 

 is probably no more than should have been gathered by the ice from the 

 supply of weathered material or geest which the ice found ready to its 

 grasp in the district immediately northward. The valley-heads moraine 

 is probably much less in amount than the mass of drift lying in the 

 drumlin belt on the low ground between the Finger lakes and lake 

 Ontario, and there are no heavy moraines south of the valley heads. 

 Where is the immense volume of drift which would have been produced 

 by excavation of the valleys to depths of hundreds of feet, by the Wis- 

 consin or any other ice sheet? 



Idea of rock basins an assumption. — No real evidence has ever been 

 presented to show that the lakes are not entirely due to barriers of 

 drift ; or, in other words, that the rock bottoms of the valleys are not 

 graded from their sources, south of the present valley heads, to the On- 

 tario valley or to their trunk valleys. In figure 4 is shown the relation 

 in vertical plane of the bottoms of Cayuga, Seneca, and Ontario valleys 



Ocean levet 



■54ft Greatest depl-h of Caijuga 

 • 175ft Greahesr depth of Seneca 



Greatest depth of onfarro -492 ft. 



Figure 4.— Diagram showing Vertical Relation of Cayuga and Seneca Valleys to Ontario Valley. 

 Vertical scale about 100 times horizontal. 



at the present time. This shows a gradient from the deepest part of 

 Seneca (somewhat south of the middle of the lake) to the abyss of On- 

 tario of about 5 feet to the mile. Any filling of drift in the Seneca basin 

 that would reduce this gradient for the rock valley may be offset by the 

 probable drift in the Ontario basin. There seems to be nothing in our 

 knowledge of the lake basins inconsistent with the idea of preglacial 

 free northward drainage. Well borings will probably prove the fact of 

 graded valleys of originally high gradient. 



