1885.] NATURAL SCIENCES OF PHILADELPHIA. 173 



gists the opportunity of studying in the field the margin of the glaciated 

 area of Pennsylvania. 



How could any area of water, still or flowing, accumulate along the 

 margin of an ice sheet which rests against an upward slope, as it so often 

 does in this State? And if such areas of water did exist south of the 

 moraine, why have not some relics of such a body of water been left in the 

 shape of sand, gravel or clay? There is no fact in relation to glaciation 

 more sat : sfactorily determined in the writer's "Report on the Terminal 

 Moraine" than the absence of any body of water, deep or shallow, in 

 front of the moraine. This unexpected fact is clearly shown by the entire 

 absence of drift south of the moraine except in river valleys (the narrow 

 glacial "fringe," elsewhere described, is excepted). While kames and 

 many other deposits made by melting ice abound immediately back of the 

 moraine, all these stop abruptly at the moraine, and the line of demarka- 

 tion is at times so sharp that "it is almost possible to stand with one foot 

 upon the glaciated and the other upon the non-glaciated ground " (Second 

 Geol. Surv. of Pa., Z, p. 103). 



The study of glacial phenomena is in a much more advanced stage in 

 America than it is in Europe. To the smaller areas studied, and to the 

 artificial changes which have modified the surface deposits of the Old 

 World, are in great part due the limited views, the confusion of terms, and 

 the contradictory theories which characterize much of the very voluminous 

 literature of the glaciation of Europe. No better field for the prosecution 

 of glacial studies can be found than in America, where single deposits 

 extend for thousands of miles under varying conditions of mountain and 

 valley, of flood plains and of prairies, and where in many places they stand 

 to-day almost in the form in which they were originally made, untouched 

 by the hand of man, and gently dealt with by that of time. 



