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NEW YORK STATE :MUSEUM 



in the middle portion of the falls the rocks have been worn and 

 broken so that the angle of fall is less than that of the dip and in 

 places the falling water has the character of a cascade. At about 

 one-third of the width of the river from the left bank there is a 

 projecting mass of smoothed rock over which little water passes. 

 At the inner side of this mass the volume of falling water is greater 

 than elsewhere and at the base there is a deep pool of water 

 occupying, a depression worn into the rocks. 



Fig. 7 Block diagram of the Cohoes region of the lower Mohawk. The 

 development of the topographic features here shown is explained in the 

 text. 



Below the falls the river flows on a bed of jagged rock but with 

 slower currents, descending in the course of a mile from the level 

 of 60 feet at the foot of the falls to 51 feet at the head of the 

 lower rapids where the river divides into three streams forming 

 the islands on the floor of the Hudson valley. In the summer 

 when the river is low most of the water below the falls is confined 

 to a deep-water channel which extends from the deep-water pool 

 at the falls. 



In interpreting these features it is to be remembered that in 

 this portion of its course the ^fohawk flows across the ancient 

 rock valley of the Hudson. The outer boundary of this rock valley 

 is clearly indicated by the ridge (although now mostly covered) 

 extending north and south from Crescent station. The postglacial 

 Mohawk river broke through this boundary at Crescent. Then 

 bending southward, its course partly determined by the strike of 



