130 G. K. GILBERT GLACIAL SCULPTURE IN WESTERN NEW YORK 



more prominent by excavation along its base and by the general degra- 

 dation of the lowland it overlooks. 



The district exhibits a marked contrast between the extent of erosion 

 from a broad mass of limestone on the one hand and a broad mass of 

 shale on the other, the ratio being, roughly, as 1 to 10 or 1 to 20. 



