F. Carney — Wave-out Terraces in Keuka Valley. 327 



"Wisconsin ice-dammed lakes would be expected. The sweep 

 of an ice-invasion, followed by the destructional work of the 

 slowly falling- bodies of water marking the period of ice-reces- 

 sion, would necessarily modify, remove or cover such features 

 as terraces in unconsolidated materials, as bars, spits, cusps, 

 etc. ; whereas the cliffs and terraces in rock would be much 

 less altered. 



The potency of ice as a factor in erosion does not make an 

 identical appeal to all observers ; this is when the sculpturing 



Fig. 1. View just north of Dunning's landing. Terraces No. 2 and No. 

 3 show here. The steepened slope nearest the lake may represent the lowest 

 terrace altered by ice-erosion. 



of bed-rock is under consideration. So it is possible that all 

 will consent to the general, though not complete, removal by 

 erosion of the constructional products of lake waves and cur- 

 rents. As a matter of field study, however, it may as well be 

 granted that these constructional forms have been entirely 

 obliterated ; the differentiation of a bar, or delta belonging to 

 some pre-Wisconsin lake, from the water-laid portions of gla- 

 cial drift would require an environment unusually free of 

 other deposits. But we must grant that cliffs and terraces 

 formed in rock would be less affected by glacial erosion. 



The extent to which these cliffs might be modified by erosion 

 would depend upon their topographic relations. Ice abrasion 

 is more effective on the slopes opposed to ice motion ; it is 

 more effective also alono; the lower contours of the walls of the 



