86 WILLIAMS — ON KANSAN DRIFT IN PENNSYLVANIA. [April 1, 



himself with respect to origins near Lake Superior and Labrador. 

 It was a surmise only, as he states that these need not have been 

 origins, and the ice may have traversed them from some more 

 northern point. The first distinct proof of sucli difference of 

 origin rests with the writer. 



This glacial deposit of East Warren disposes, also, of another 

 question which has been much debated, whether there was more 

 than one ice age. 







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The writer has already disposed of the question for eastern Penn- 

 sylvania, by showing that the Lehigh and its tributaries acquired 

 their present level in pre-Kansan times. The lenticule at East 

 Warren was about loo feet above the present Allegheny; but the 

 rock floor, as shown by a well section near, was 120 feet below the 

 lenticule, or twenty feet below the present Allegheny. Other well 

 sections show that this floor is dipping steeply and toward the 

 west, so that it reaches greater depths below the present river level. 

 This lenticule was forty feet below the old surface at this point; but 

 this surface rose on going west, so that in a distance of fifty feet 

 it was sixty feet higher. On this old surface the various geologists 

 have collected material and all agree that it represents the oldest 

 glacial period. This surface is one of the alleged **rock shelves " 

 of the region ; but is instead a dump in slack water and shown by 

 well sections to be over 250 feet thick. It is allowed by all that 



