SOILS OF NEW YORK 91 



the general path of movement of the ice; third, that 

 throughout the southwestern two-thirds of the State, 

 the general slope of the land is to the north. As a 

 result of this condition, ponds and finally great 

 lakes were formed in the hollows between the front 

 of the ice and the northward slope of the land as the 

 ice gradually retreated northward due to melting. 

 Xaturally, the water accumulated in the valleys and 

 sooner or later attained a level that permitted it to 

 drain oif to the southward in the form of great swol- 

 len rivers. The valleys of the Delaware, Susque- 

 hanna and Allegheny rivers bear evidences of this 

 former ilood level in the remnants of gravel, sand and 

 silt that form terraces along their courses. 



As a consequence of the three sets of facts just 

 pointed out, there has been very extensive mixing of 

 the rock material from different formations. In gen- 

 eral, the material from each rock formation is most 

 abundant to the southward of its exposure. This 

 feature of the distribution of rock material is es- 

 pecially important to keep in mind in considering the 

 occurrence of limestone which has a very large in- 

 fluence on the crop-producing capacity of the soil. 

 In a glaciated region there is not necessarily any 

 close relation between the underlying rock and the 

 soil material that rests upon it. The soil has prob- 

 ably been brought in from a greater or less distance. 



The unconsolidated earth above the bed rock is 

 extremely varied in thickness, in fineness, in content 

 of stone, in color, and content of organic matter, in 

 content of limestone, in drainage, and as a result of 



