rl22 NEW YORK STATE MUSEUM 



StO'Ckbridge and Eaton Mils the notches are conspicuous profile' 

 features even at great distances. When the streams were con- 

 fined in rock walls, they intrenched themselves in the rock and 

 sometimes cut ravines of large dimensions (see p. 123, 124). 



3 It will be understood that the cutting of a ravine or the exist- 

 ence of cascades and cataracts implies that the lake or land w^hich 

 received the overflow must have had a level below that of the 

 tributary lake or stream by at least as much as the amount of 

 fall. We shall make use of this principle later, in our study of 

 the order of retreat of the ice front and of the time relation of 



the channels. 



Lower and later channels 



The lower channels of the first three groups were not cut by the 

 drainage of local waters, but by overflow of the great lake Warren 

 and the hypo-Warren waters. All the channels of the fourth, 

 fifth and sixth groups were cut by local waters. However, north 

 of these groups, on the lower ground, there are channels which 

 were made by the hypo- Warren (better called hyper-Iroquois) 

 waters. These lower channels lie north of Chittenango, at and 

 south of Canastota, through Oneida, and toward K^ome. The New 

 York Central railroad follows here the smooth level stretches 

 swept by the great rivers that preceded the beginning of Lake 

 Iroquois. These later channels are outlined only by their south 

 banks, as the rivers flowed along the ice margin which consti- 

 tuted their north bank. The stream-cut cliffs which formed the 

 broken south banks of the rivers, may be seen from the New York 

 Central and the West Shore railroads. These latest channels 

 will be the subject of future study. 



Ravines and cataracts 

 Some of the deeper channels in the limestone are of such form 

 and depth that they might be called canyons. Some of them are 

 headed by vertical cataract cliffs, the plunge basins of which in 

 several cases now hold lakes (pi. 25-35). The largest of these 

 gorges were cut by the hypo-Warren waters, and with their cata- 

 ract phenomena were in a true sense the predecessors of Niagara 



