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



Adverse philosophy. — The considerations presented above bear di- 

 rectly on the local problem, and they should alone be convincing of 

 the fact that the Finger Lakes, valleys were never deepened by ice ero- 

 sion. The general theoretic argument against the competency of ice to 

 deepen valleys has been purposely waived to this moment in order to 

 give force to the concrete phenomena, but it should now be emphatically 

 stated that the theoretic objections outlined on pages 25-31 apply with 

 special force to this case. Theoretically there never could have been 

 any effective cutting by ice in the deep bottom sections of Seneca and 

 Cayuga, and really there are no phenomena nor features of any sort 

 which require or even strongly suggest it. 



Direct proofs of non- erosion. — Finally and conclusively we have in the 

 valleys of the Finger lakes the same indisputable evidence of lack of 

 ice erosion which has been described for the Niagara escarpment. In 

 quarry exposures along the Seneca and Cayuga valleys and elsewhere, 

 it may frequently be seen that the upper layers of rock are weathered 

 and rotted far beyond what is possible since the ice retreat. Abraded 

 surfaces of fresh rock of the same kind, in the same localities, even in 

 the same exposures, give comparison for postglacial decay which for 

 till- protected surfaces is practically nothing. 



Preglacially weathered rock in position may be recognized in a vast 

 number of quarries or freshly cut rock sections throughout western- 

 central New York. In the Finger Lakes district the rocks are chiefly 

 shales, which are not favorable for preservation or discrimination of the 

 old decomposition product. Fortunately there are numerous limestone 

 quarries along the belt near the north ends of the valleys, and a few 

 openings in the Tully limestone toward the upper end of at least the 

 Cayuga valley ; and limestone preserves the record in perfection. 



To one on the ground the evidence is perfectly clear, but the photo- 

 graph does not give the differences in color and texture nor show the 

 finer effects of solution and corrasion. However, the facts are well 

 shown in plates 22 and 23, which are only a few examples from many that 

 might be given. 



Plate 22 gives an example from the Onondaga valley similar to the plate 

 18, from Buffalo. This is a photograph of the east side of the Indian 

 quarry, about 7 miles south of the center of Syracuse. The elevation is 

 580 feet and only about 120 feet above the bottom of the valley. The 

 east wall of the valley rises 800 feet above the quarry. The preservation 

 of the finest striae and polishing of the limestones beneath even a thin 

 mantle of till proves the incompetency of postglacial weathering to pro- 

 duce the degree of corrasion found in upper layers. In some parts of 



