PRIMARY ROGKS» 
543 
are gradual, and slope gently to the surface, and disappear. Butter hill and Woodcock 
mountains are exceptions to the above appearances ; but even Butter hill, steep as it is, has 
not the ragged broken appearance which many southern terminations exhibit.”* 
Gneiss is the prevailing rock of the Highlands. It passes into hornblendic gneiss and^ 
hornblende rock on one side, and into micaceous gneiss and mica slate on the other. The 
latter is very rare, while the micaceous gneiss is more common, and the hornblendic gneiss 
is one of the most common rocks. 
Granite is very abundant, both in beds and veins. That in beds is often twenty to forty 
feet thick, of a coarse grain with a base of red felspar, and often contains ndularia and 
epidote. Examples may be seen near the landing at West-Point, and in that vicinity. The 
granite of the caps of the hills and mountains is frequently of a finer grain, sometimes suit¬ 
able for a building stone. The granite in veins is generally of a still finer grain. There 
seems to be little regularity in the direction of the veins, but perhaps a majority of them 
intersect the strata nearly at right angles, paratlel to the direction of one set of the joints that 
have been described whTile treating of the rocks of the New-York System. 
The dip of the rocks is very variable. In many places the strata are nearly or quite verti¬ 
cal, in others they are nearly horizontal, and they vary indefinitely between these limits, and 
are in some places contorted, so as in short distances to show every, possible amount and di¬ 
rection of dip ; but notwithstanding these great variations, the prevailing dip is to the E.S.E. 
from 30° to 70°. 
The general line of bearing of the strata in the Highlands and Westchester and New- 
York counties is north-northeast and south-southwest, and this direction approximates to the 
direction of the hills and mountains ; but these latter, as has been before stated, are not unin¬ 
terruptedly continuous in any place more than a few miles. 
There are many localities where the line of bearing has been mentioned as transverse to 
the general direction, ranging between west and northwest, with a dip to the north, north- 
northeast and northeast. The facts connected with the transverse lines of bearing and of dis¬ 
turbance and faults will be mentioned in another place, when treating of axes of elevation and 
disturbance. 
Local Details. 
These are selected from a great number of observations, as having some interest; some in 
an economical point ef view ; some for those who will examine the localities ; some in eluci¬ 
dating the particular local geology ; and some as having a bearing on various points of phy¬ 
sical geology, which may be useful to those who may have time and opportunity to trace out 
the lines of disturbance with which they are connected. 
The subjoined table exhibits the kinds of rocks seen on the shore from Peekskill to Anthony’s 
Nose point, and thence up the Hudson to the point northwest of the “ Old silver mine,” along. 
* Annual Geological Report of New-York, 1839, p. 188, 139. 
