1892.] NATURAL SCIENCES OF PHILADELPHIA. 469 



EXTRA-MORAINIC DRIFT IN THE SUSQUEHANNA, LEHIGH AND 



DELAWARE VALLEYS. 



BY G. FREDERICK WRIGHT. 



In the autumn of 1880, the late Professor Henry Cavvill Lewis 

 and myself began the exploration of what we supposed was the 

 boundary of direct glacial action in Eastern Pennsylvania. The 

 work of field exploration was substantially completed in 1881. Our 

 report constitutes volume Z in the series published by the 2d 

 Geological Survey of Pennsylvania, and appeared in 1884. 



After accepting with little question the delineation of the terminal 

 moraine from the New Jersey report for that State, we began work 

 in Northampton County, Pa., and soon succeeded in tracing a well 

 marked moraine across the county from near Belvidere, in New 

 Jersey, to the vicinity of Offset Mountain, in the Kittatinny Range, 

 a few miles northeast of the Wind Gap. At that time our attention 

 was not sufficiently directed to the more dispersed erratics and thin- 

 ner glacial deposits Avhich usually extend in advance of the moraine, 

 and which, subsequently, Ave came to recognize as the " fringe." The 

 facts concerning the " fringe " came prominently to light in connec- 

 tion with ray own further investigations in the western part of 

 Pennsylvania, and in my own investigation in the States far- 

 ther west. In my reports on that region I soon ceased to give 

 special attention to moraines, and confined attention to the border 

 of the fringe, and in my map in the volume " The Ice Age in 

 North America," the legend indicating the terminal moraine across 

 Pennsylvania, gives place in the States further west to one marking 

 the southern limit of the ice sheet. 



In view of these facts it is significant that in his report (p. 201), 

 Professor Lewis uses this language : " It is possible that traces of 

 this fringe might be detected in Eastern Pennsylvania and in New 

 Jersey. In fact, occasional transported boulders do occur upon 

 several hilltops, just in front of the moraine, in the vicinity of the 

 Susquehanna and Delaware rivers, and in New Jersey, which I find 

 it difficult to explain on any theory of a flood, and which may be 

 of like origin with the fringe as developed farther west. Facts 

 observed by other geologists in more western States, and published 

 since this report was written, confirm my impression that this fringe 

 is destined to play an important part in glacial geology." 



