The Glacial Origin of Cliffs — Davis. 
15 
and this ancient low-land has been in post-Cretaceous time 
bodily elevated and greatly eroded, the softer bedded rocks hav¬ 
ing been thereby reduced nearly to another lowland on a second 
base-level, bl, fig 2, seen in the low country between the present 
ridges, while only the crest-lines of the strongest trap ridges 
remain to testify to the first base-level bl. Still another eleva¬ 
tion of moderate amount is noted in New Jersey, but not in 
New England. There is reason to think that the chief ones 
of these processes were practically contemporaneous from 
Massachusetts to Pennsylvania, and the rocks throughout are 
so much alike that we should expect the topographic profile of 
the two districts to be closely similar; and indeed so it is, except 
in the detail of cliff and talus. 
We may briefly consider the general development of the talus 
before questioning whether the New England ridges owe their 
present form to glaciation. The talus is a special form taken 
temporarily by the waste of the land on its way to the sea. 
