438 NEW YORK STATE MUSEUM 



a blanket of Paleozoic sedimenits probably covered the entire 

 region, these original streams soon became superimposed streams, 

 and showed no adjustment to the Precambric rocks which they 

 uncovered in their beds during the stripping away of the Paleozoic 

 cover. The present valleys are largely adjusted to these rocks, 

 and this adjustment has been brought about by the successive 

 uplifts of the region, each new cycle of wear tending to miake it 

 more perfect. The adjustment is in part on the weak rock belts 

 and in larger part on the weak rock structures. 



The Champlain valley has been shown to be a structural one, 

 and as such to be the inevitable site of a drainage system. The 

 subsequent origin of the Mohawk and Black rivers has also been 

 indicated and had been previously emphaisized by Brigham and 

 others. The St Lawrence valley has alsio the character of a sub- 

 sequent valley, as was first pointed out by Westgate; but, as it 

 was the site of an old Paleozoic trough of depression and deposit, 

 which seems to have been; deepened by subsequent movements, this 

 would appear to have had some share in determining its position. 

 With successive uplifts of the region, the Mohawk and Black river 

 valleys move laterally outward. This is not the case with the 

 Champlain valley. 



The outflowing Adirondack istream® of the present are thus all 

 tributary to streams which parallel the sides of the region. Those 

 outflowing to the west and south are but the remnants of the con- 

 sequent streams which continued on in those directions before the 

 development of the Mohawk and Black river valleys, as Brigham 

 pointed out. They rise near the main axis of elevation and flow 

 in valleys cut in its gentle westerly slopes. Beginning at the 

 southwest with West Canada creek, appareutly only recently 

 transferred to the Mohawk drainage from the Black, all the west- 

 erly streams, the Moose, Beaver, Oswegatchie, Grasse, Raquette, 

 St Regis, Deer, Salmon and Chateaugay rivers, have this general 

 character. All have been affected and modified by the ice sheet; 

 but these modifications are local, and otherwise these streams 

 rise near the main axis of the region and course down its westerly 

 slopes, to the southwest, the west and the northwest. The abrupt 



