32 N. H. Darvton—Shawangunk Mountain. 
there is a corresponding increase of erosion in the soft underly- 
ing shales, which beyond certain mits causes rapid recession. 
This is illustrated by Sams point, where the maximum altitude 
of 2,240 feet is attained. The “ point” is a narrowing extension 
of the grit along the axis of a very flat synclinal, which finally 
terminates in a high narrow cliff presented southward. From 
the wide anticlinal area to the west the grit has been eroded and 
the Hudson shales occupy the surface in a group of very high 
hills. These hills are surrounded by cliffs of the grit which on 
the eastern side rise somewhat above their summits, on the 
northern are about even with their higher summits, and on the 
western lie along their flanks. Originally the grit area in this 
region and southward was as wide as it is now at lake Mo- 
honk, but owing to the greater height to which the northern 
pitch of the flexures carried the grit, it was here more rapidly 
and widely undermined and removed. It is the grit on the 
western limb of the anticlinal that lies on the western flanks of 
the shale hills, constituting a monoclinal ridge of considerable 
prominence which extends from Ellenville far southward into 
Pennsylvania. This monoclinal mountain consists of a single- 
crested ridge of the Shawangunk erit, with a long slope up the 
dip from the valley westward, which terminates in an east- 
facing cliff of grit surmounting long rolling slopes of shale on 
the eastern side of the mountain. Its structure near the southern 
edge of Ulster county is shown in the bottom section on the 
stereogram, and this is typical for the greater part of its course. 
In the valley westward there is a succession of formations overly- 
ing the grit, as shown on the left of the sections in plate 1. They 
are the Clinton red shales, Salina water lime, Helderberg lme- 
stone, Oriskany sandstone, Esopus shales, Onondaga limestones, 
and a great mass of Devonian shales and sandstones which ex- 
tend into the Catskills. The dips along the western slope of the 
mountain are low north of Wawarsing, but they rapidly increase 
southward to an average of about 60° in the vicinity of Ellen- 
ville. In this region of steep dips the streams flowing down 
the steep western slope have cut deep gorges, which extend 
through the grit into the underlying shales. The two streams 
south of Ellenville are exaggerated examples of this, and they 
have been largely instrumental in baring the Hudson shales on 
the anticlinal area behind Sams point. The two streams just 
north of Ellenville also cut into the shales, but they are very 
