54 



WILLIAMS— DEEP KANSAN PONDINGS IN 



This dam was in the narrower and more crooked North Branch 

 of the river : the one in the main stream and far broader valley was 

 low ; but sufficient to form a terrace that runs, with slight rise, for 

 lo miles up the valley of Middle Creek, and for 20 miles up that of 

 Penn's Creek. The latter has a delta i mile broad. ^ This low ter- 

 race is the nearest approach to a complete valley filling that we shall 

 meet with. 



Juniata Ponding. 



I. C. White^ was the first to describe the glacial outwash in 

 Juniata Valley, and to call attention to the great distance above the 

 average level of the gravel terrace to which sporadic patches of the 

 same were carried. E. H. Williams, Jr., in 1895,* ascribed their 

 origin to ice-dams in the many " Narrows " where this stream has 

 cut through the more resisting ridges which border the trough-like 

 valleys it crosses in its way to the Susquehanna River. The terrace 

 runs with but slight rise far up the valleys of its affluents, and the 

 sporadic gravels are the usual iceberg trash carried on the crest of 

 the released wave when an ice-dam broke, and permitted the ponded 

 water to rush up all opposing slopes and leave its bergs and their 

 burden. This phenomenon occurs nearly every spring in northern 



Fig. I. Outwash from Lake Lesley, south of saddle, at East Tyrone. 



