Studies for Students. 



THE DRIFT — ITS CHARACTERISTICS AND 

 RELATIONSHIPS. 



Contents. 



Definition of the drift. 

 Thickness of the drift. 



In general. 



Along its borders. 

 Driftless areas. 

 Constitution of the drift. 



Physical heterogeneity. 



Lithological heterogeneity. 



The fine material of the drift. 

 Structure of the drift. 



Stratification. 



Foliation of the unstratified drift. 

 Shapes and markings of the stones of the drift. 

 The sources of the drift. 



Definition of the drift. The northern part of the United States, 

 as well as a large part of the Dominion of Canada, is covered 

 by a mantle of incoherent materials composed of clay, sand, 

 gravel and bowlders. These various materials are sometimes 

 intimately commingled, and sometimes more or less dis- 

 tinctly separated from one another. The separation may be 

 either lateral or vertical. One region may be covered by 

 well-assorted gravel or sand, while a contiguous area may 

 be covered by bowlder-bearing clay, or by an unassorted mix- 

 ture of bowlders, gravel, sand and clay ; or layers of sand and 

 gravel may alternate with layers of unassorted bowlder-bearing 

 material in the same vertical section. Where bowlders, gravel, 

 sand and clay are associated without trace of separation or 

 arrangement, any one of them may predominate over the others 



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