GLACIAL GEOLOGY OF THE SARATOGA QUADRANGLE 29 



Evidences that the present Hudson channel from Corinth eastward 

 is of recent geological origin are as follows : ( i ) at Corinth the 

 river enters a gorge cut into stratified rocks of the Cambric period 

 whose vertical walls (as seen on the south side) are about 60 feet 

 high; (2) there is a fall of 220 feet in the bed of the river from 

 Corinth to the place where the river emerges from the Adirondack 

 region upon the level tract of the Hudson plain, a distance of about 

 12 miles; (3) the valley is in general narrow, with steep slopes, and 

 all the tributary streams are small and have steep gradients ; (4) the 

 river has cut away the eastern end of the morainic belt and divided 

 the lacustrine deposits north of it; (5) "the present course of the 

 Hudson from the eastern edge of the Adirondacks to Fort Edward 

 is evidently of postglacial origin, for the river runs over ledges at 

 Fort Edward, at Baker's Falls, at Sandy Hill and again at Glens 

 Falls, dropping from the 300 foot contour at the edge of the moun- 

 tains to about 130 feet at Fort Edward." 1 



There are, however, other features of the valley which constitute 

 evidences that it is not wholly postglacial in origin, that is, has not 

 been formed wholly since the latest withdrawal of the ice to the 

 north : ( 1 ) Although the river intersects a mountainous region, 

 there has been but a slight development of rock gorges. Excepting 

 the gorge at Corinth and a shallow rock channel at Spiers falls (lo- 

 cated about a mile below the mouth of Stony brook) the valley 

 walls are nowhere vertical and cut in rock, as is typically the case 

 with postglacial streams ; for example, the Mohawk river at Little 

 Falls and at Aqueduct, 3 miles below Schenectady. In general the 

 valley is V-shaped in cross-section. (2) The river has cut its valley 

 largely in till. Beginning at the lower end of the gorge, at Palmer, 

 the valley walls for several miles are composed of till, with few ex- 

 posures of the underlying Precambric rocks. The creek that flows 

 from Palmer down the slope to the river has its bed on till. Below 

 the mouth of the creek the valley wall, especially at its lower levels, 

 is thickly strewn with boulders. In places the wall of the valley is 

 somewhat terraced and many boulders of large size lie on the terrace 

 faces. In other places the valley wall slopes to the margin of the 

 river and along the shore are many large boulders which have accu- 

 mulated from rolling or sliding. The materials of the slopes of the 

 river, farther on in its course, are till ; excepting that near the bend, 

 at the upper level of the slope, on the right bank of the river, the 

 terrace of lacustrine deposits, already referred to, occurs, and south 



1 Woodworth, op. cit., p. 75. 



