GEOLOGY OP THE NORTHERN ADIRONDACK REGION 433 



identical. There are several cases in which, the presence of the 

 scarp can not possibly be owing to differing rock resistance, so 

 that the only element of doubt in the matter concerns the actual 

 existence of the faults. They are very difficult to prove under 

 suQh circumstances, yet it seems practically certain that they 

 must be there. 



North plain 



On the north side of the Adirondacks a gently sloping plain 

 extends from the Precambric boundary down toward the St 

 Lawrence. It is warped upward along the north extension of 

 the main axis of elevation, hence has a northerly pitching axis 

 along this line, with northeast and northwest surface slopes 

 away from it. These are but gentle, some 20 feet to 30 feet to 

 the mile. The underlying rocks are the Potsdam and Beekman- 

 town formations, which have a low, northerly dip. This is how- 

 ever considerably greater than the surface slope, amounting to 

 from 100 feet to 200 feet to the mile, so that the rock layers are 

 beveled by the plain surface, progressively higher beds being 

 exposed going north. 



The general surface has received a comparatively smooth 

 veneer of glacial deposits, supplemented by the deposits of run- 

 ning and static waters during and after the ice retreat. Low 

 moraines constitute the principal present irregularities. There 

 is no Beekmantown inface, for example, though this may be 

 lacking because of being planed down by the ice sheet. Rock 

 outcrops are so scarce in the region, however, that there is no 

 opportunity to determine whether this is the case, or whether 

 the inface has been buried beneath the drift. The old stream 

 valleys have been filled up, and the streams have since somewhat 

 reexcavated them though, since they have not accurately followed 

 the old channels, they have met rock at small depth in spots 

 where they have missed the track, and this has greatly retarded 

 the reexcavating process. The plain retains approximately its 

 preglacial slope, but its irregularities have disappeared through 



