24 RURAL NEW YORK 



mountainous country of low agricultural possibilities. 



The long period of erosion to whicli the State was 

 subjected cut the surface into a very coni])]ete net- 

 work of valleys. While the data are incomplete, the 

 indications are that the drainage was mostly to tlie 

 north and west to a great channel that occupied the 

 axis of the Great Lakes and the St. Lawrence River. 

 The topography of the southern highland was fairly 

 rough. Through the middle and eastern part it was 

 lower and in general more mild in outline than in 

 other parts. 



Into this long-eroded region there came the great 

 continental glacial ice sheet. It advanced in a gener- 

 ally southerly direction from the Labrador highlands 

 in eastern Canada. Slowly it advanced, pushing long 

 tongues forward through the valleys. It was de- 

 flected by the land forms. Having tilled the valleys, 

 the ice advanced up the slopes until it covered all the 

 mountain areas. Southward it advanced and piled 

 deeper, until all the State was covered except a small 

 angle south of the Allegheny River in Cattaraugus 

 County. The rate of movement was generally in 

 proportion to the depth and was most rapid through 

 the valleys and slower over the hills. The old re- 

 sidual soil covering was swept away. Numerous emi- 

 nences were planed off. Some valleys that crossed 

 the course of the ice were partially or wholly filled, 

 and those parallel to the ice movement were eroded 

 still deeper, giving rise to "hanging valleys," which 

 is the phenomena of side valleys high above the main 

 valleys into which they flow. 



