450 NEW YORK STATE MUSEUM 



sandstone rising in beetling cliffs, or more or less hidden by its 

 own talus from which spring forest trees and a remarkable variety 

 of ferns, and on the other hand a slope composed of black friable 

 shales, with an occasional seam of smooth jointed sandstone, in- 

 clined at a sharp angle away from the precipitous cliff across the 

 way. Lying almost perpendicularly against the foot of the lime- 

 stone cliff are layers of very black, slaty shale undoubtedly belong- 

 ing to the Utica though the shales seen in the slope across the high- 

 way are from the presence of layers of sandstone and their general 

 lithologic characters, Hudson river. If the approximate base of 

 the Hudson river is near the foot of the escarpment then taking 

 the thickness of the Utica stage as 1200 feet there is a displace- 

 ment here of over 1300 feet. 



Northward from the " hollow " the escarpment becomes less pro- 

 nounced though quite distinct for some miles farther. To the north 

 the Trenton has been eroded from the Calciferous and the country 

 to the east of the fault Une is flatter so that there is not the decided 

 contrast of formations. One may however see at various points 

 the shales of the Utica or Hudson in fairly close connection with 

 the massive sandstone of the Calciferous. A case of this sort 

 occurs at a point 4.2 miles north of the Mohawk river. South of 

 the river the line is nowhere as distinct as on the north side. It 

 is however to be determined within a fair approximation as will 

 be seen in another part of the present paper. The course of the 

 Sandseakill may be in part determined by the presence of the fault, 

 a supposition which is at least suggested by the topography of the 

 locality. 



East of the Sandseakill rises the high hill back of Rotterdam 

 Junction. This hill is a conspicuous object to one looking at the 

 sunset from the campus of Union college, its summit rising more 

 than 1000 feet above the Mohawk at its foot. Just east of this hill 

 flows the Plotterkill, a stream heading near Mariaville and reach- 

 ing the Mohawk through a deep glen a mile and a half east of 

 Rotterdam Junction. A short distance west of the mouth of the 

 Plotterkill is the mouth of a small creek which flows down the 

 northeastern slope of Waterstreet hill.^ The shales and sandstones 

 of the Hudson river stage are exposed in this creek for several 



^On the U. S, geological survey's Amsterdam topographic sheet a triangulation bench 

 mark is indicated on the northwestern brow of the hill at an altitude of 1279 feet A. T. 

 and denominated Waterstreet. 



