ANCIENT GLACIERS. 87 



valleys into which the creeks empty at either end; and 

 there are numerous kettle-holes and lakelets in the vicini- 

 ty, such as characterize the glacial region in general. 



In short, we are, without doubt, here on a well-marked 

 terminal moraine much modified by strong water-action 

 in a valley of glacial drainage. The gravel and boulders 

 are all well water- worn, and the material is of various kinds, 

 including granite boulders from the far north, such as char- 

 acterise the terminal moraine on the highlands ; but the 

 pebbles are not scratched, and the gravel is more or less 

 stratified. It is evident that we are here where a violent 

 stream of water poured forth from that portion of the ice- 

 front which filled this valley, and which found its only out- 

 let in the direction of the Lehigh River. The gravel can 

 be traced in diminishing quantities to the southward, in 

 accordance with this theory, while to the northward there 

 extends a series of gravel ridges, or kames, such as we have 

 shown naturally to owe their origin to the accumulations 

 taking place in ice-channels formed near the front of a 

 glacier as it slowly melts away. 



From similar occurrences of vast gravel accumulations 

 in other valleys stretching southward from the glacial 

 margin, we came to expect that, wherever there was an 

 open, line of drainage from the glaciated region south- 

 ward, the point of intersection between the glacial margin 

 and the drainage valley would be marked by an excessive 

 accumulation of water- worn gravel, diminishing in coarse- 

 ness and abundance down the valleys in proportion to the 

 distance from the glacial margin. 



For example, the Delaware River emerges from the 

 glaciated region at Belvidere, and there are there vast ac- 

 cumulations of gravel rising a hundred or more feet above 

 the present level of the river, while gravel terraces, dimin- 

 ishing in height, mark the river below to tide-water at 

 Trenton. The Lehigh River leaves the glaciated region 

 at Hickory Run, a few miles above Mauch Chunk, but 



