200 PROCEEDINGS OF THE ACADEMY OF [1895. 



the Delaware enters that portion of the Water Gap that I believe 

 is the work of the present south-flowing river. 



Nor is the character of the part of the Gap just described the 

 only evidence that the Delaware River in pre-glacial times flowed to 

 the northward. 



In Vol. G6, page 53, we read, "finding an old buried valley bed 

 from Port Jervis northeastward to the Hudson River at Rondout, 

 * * * the suggestion seemed not unreasonable that the Delaware 

 turned northeastward at Port Jervis and, receiving a large tributary 

 from the south, kept along this old buried valley to the Hudson River. 

 "But," the report continues, " subsequent study of the Delaware 

 Valley, southward * * * seemed to render this view uncertain, 

 .since the Delaware appears to have flowed through the Kittatinny 

 Mountain, at the Water Gap, during its entire history." 



I think it is clear "the Delaware has flowed through the Gap 

 during its entire history," but that the direction of the flow of the 

 river through the Gap in pre-glacial times was exactly the reverse of 

 its direction since the glacier disappeared. 



In Vol. D3, of Penn. Geol. Sur. Rept's., two remarkable patches of 

 gravel are described. One is at West Bethlehem, the other at 

 Easton. Both lie at a height of 170 feet above the present level of 

 the water in the Delaware at Easton. Upon this gravel rests a 

 boulder clay which contains scratched stones, gravel and clay, to- 

 gether having a thickness of from 25 to 30 feet. The irregularities 

 of the upper line of the gravel are great and show it was worn into 

 hollows before the clay was deposited. " This gravel," says the 

 report, "is unquestionably a river deposit, a fragment of an ancient 

 river terrace, and could only have been formed by the damming 

 back of descending waters; but there is no evidence of such a dam 

 and no known means for producing it below Easton." 



If the Delaware, at the time it was depositing this gravel was 

 "descending" towards the north, then it is above Easton and not 

 below that we must look for the means for producing such a dam. 



I think we can find both the "means" and the place, and that 

 they explain not only the gravel but also the boulder clay which 

 li<s on top of it. The "means" is the great Ice Sheet, moving 

 southward ; the place, where this Ice Sheet effectually blocked the 

 northward flow of the Delaware. This, undoubtedly, would be at the 

 Water Gap. But, manifestly, a great river flowing far to the north- 



