20 NEW YORK STATE MUSEUM 



In the upper portion of the gorge above the bridge the north wall 

 for some distance is a rusty, pinkish rock of fine grain and rather 

 massive appearance. It resembles certain phases of the basal quartz- 

 ite which have been noted outside the quadrangle, particularly the 

 outcrops in the brook crossed by the mountain road a mile south of 

 Dutchess Junction. This rock is jointed, and rests upon the gran- 

 itic derivative of the Bald hill gneiss. 



Bald hill. The rock composing this spur of the Highlands was 

 carefully examined along its base while tracing- the quartzite, and 

 also in two sections across its summit from west to east. One of 

 these sections was made across the northern portion of the spur 

 along an old wood road leading from the lane southeast of the 

 Maddock farm near Glenham station. The other was taken partly 

 along the road ascending Mount Beacon, then bearing to the left 

 past the Graham place through " Hell Hollow " to the Cold Spring 

 road. The rocks in the quarries near Mount Beacon reservoir, and 

 in the excavations made for the new house at the summit of Beacon 

 during the summer of 1908, as well as the section along the road 

 descending from the reservoir to Matteawan, were studied. Com- 

 parisons were made with the outcrops along the base of the ridge 

 to the quarry at Storm King station and in the railroad cuts from 

 Storm King to Cold Spring. An examination of other parts of the 

 ridge of which Bald hill is the northern extremity, was necessary 

 in order to form a clear idea of the character of the gneiss. 



Along the northwestern slope of the spur the gneiss is mainly a 

 medium-grained, laminated hornblende rock with some micaceous 

 variations. Along the basal portion of this slope the gneiss is usually 

 rusty from included iron stains. Higher up it is commonly a drab 

 or gray rock. The laminated character is more noticeable and the 

 laminations are finer along the basal portion of the northwestern 

 slope. Throughout most of the mountain the gneiss is rather 

 coarsely or indistinctly foliated and in places is quite massive and 

 granitic in appearance. 



The characteristic rock of Bald hill, as just described, is identical 

 in texture and mineralogy with the rock in the quarry at Storm 

 King station and with the prevailing type in the railroad cuts be- 

 tween Storm King and Cold Spring. It is the chief variety in the 

 quarries at Mount Beacon reservoir. 



At the excavations for the new mountain house on Beacon, the 

 drab-colored granitic gneiss passed into a variety composed of 

 white feldspar and hornblende. In the hollow between Beacon 



