GLACIAL WATERS IN CENTRAL NEW YORK 



31 



the face of the escarpment have been given names and altitudes by 

 Dr Spencer as follows [see title 42, p. 197]: Roy, 533, 521 feet; 

 Eldridge, 446; Bell, 420. To make comparison with the eastern 

 spillways we must add to these figures about 60 feet in order to bring 

 the Iroquois plane at Lewiston into horizontality with the same 

 plane at Syracuse. This makes the altitudes as follows: Roy, 

 593, 581; Eldridge, 506; Bell, 480 feet. 



It is possible to select separate channel summits which have fair 

 correspondence with the terrace levels, but precise comparison is 

 not of value when we consider the downcutting of the outlets ; the 

 indefinite relation of the terraces to their respective water levels; 

 the possible slight land warping; and the minor oscillations of the 

 ice barrier. It is sufficient to note that the Niagara terrace levels 

 range from 600 down to 477 feet and that the later hyper- Iroquois 

 channels range from 600 down to the Iroquois level, 440 feet. 



The excellent channel leading east from the Irondequoit valley, 

 the Fairport-Palmyra-Lyons channel, with present altitude of 460 

 feet, was probably the latest channel, correlating with the Bell - 

 terrace. When this outlet was effective the Iroquois water was 

 probably established at Syracuse, and the hyper-Iroquois restricted 

 to the territory west from Rochester [see pi. 41]. 



The volume of water carried by the channels, which was not 

 augmented by the interposition of the cataract, was comparable 

 to that of the St Lawrence. The -smaller land area then drained 

 was probably more than offset by the supply from the extended 

 front of the rapidly melting glacier. 



Onondaga valley to Limestone valley 

 This relatively short stretch of 8 miles is in one respect the most 

 interesting of all the channel districts, since it holds remarkable 

 extinct cataracts and plunge-basin 'or cataract lakes. The lower 

 and principal channels with the cataract phenomena have been 

 briefly described in former publications by the State [see titles 

 27, 28]. Some new facts are given here, specially concerning the 

 higher drainage, and the map, plate 4, depicts the earlier and 

 higher channels and gives details which the former black and 

 white sketches did not give. 



This tract covers the north ends of two great north-and-south 

 ridges separating three deep valleys. The sudden fall of the waters 

 which cut across the ridge between the Onondaga and Butternut 

 valleys produced steep ravines in the limestone and one mag- 



