524 J. H. STOLLER HISTORY OF MOHAWK-HUDSON REGION 



Ballston Channel at East Line southeastward to Bound Lake presents all 

 the features of a valley of erosion of recent origin made by broad and 

 strong currents. At its upper end the valley is wide and open in its outer 

 portion, while the middle portion forms a rock gorge with shelving walls 

 about one-eighth of a mile in width. The gorge continues to Eound Lake, 

 widening in its lower part where its walls recede into well defined rock 

 terraces. There is a fall of 112 feet from the floor of the Ballston Chan- 

 nel, taken at 300 feet at East Line, to Eound Lake — a distance of 2% 

 miles. The broadened lower end of the rock-cut valley opens into the 

 general depression at the bottom of which Eound Lake lies. The floor of 

 this depression consists largely of till, with scattered boulders, and its 

 slopes show terrace features, indicating the erosive work of sweeping cur- 

 rents. The depression continues as a broad and deep valley of erosion, 

 opening into the Hudson Valley at Mechanicville. 



The factors which determined the diversion of the Mohawk waters to 

 the Eound Lake Channel, terminating the Coveville outlet stage of the 

 drainage history of the region, were as follows : When the East Line dis- 

 tributaries were developed, the one flowing southeasterly at first pursued 

 a sluggish and meandering course across the Pleistocene deposits lying 

 over the Eound Lake region. Eventually and pari passu with the subsi- 

 dence of the lake waters, through lateral and downward cutting, the pres- 

 ent Eound Lake basin was gradually developed. The escaping waters 

 from the Ballston Channel now falling over the rim of the old rock de- 

 pression, some 100 feet lower than the rock-floor of the channel, eroded a 

 gorge which eventually, through deepening and recession, undercut the 

 main valley. As soon as this side valley had been enlarged through ero- 

 sion to the capacity of containing the volume of waters flowing in the 

 main valley the river was diverted into the new course. 



DEVELOPMENT OF THE AQUEDUCT-COHOES QORGE OF THE MOHAWK 



A similar explanation applies to the postglacial gorge of the Mohawk 

 from Aqueduct southeasterly to Cohoes. The nearly vertical wall of the 

 gorge on the north side of the river at Aqueduct is marked at its summit 

 by the 340 -foot contour. Back of the summit there is a marginal eroded 

 area rising to the 360-foot level or somewhat higher. South of the gorge 

 the wall of the valley is of equal height, When the Iroquois-Mohawk 

 waters were first diverted into the Ballston Channel a place of overflow 

 of the waters over the margin of the channel at Aqueduct was developed. 

 This may have been clue to the wall at this place having been slightly 



