PRIMARY ROCKS. 
549 
rocks continue nearly the same to West-Point, and dip east-southeast sixty to ninety degrees. 
On the turnpike from Coldspring to Carmel, the rocks are gneiss and micaceous gneiss, 
hornblendic gneiss with beds and veins of granite, greenstone and hornblende rock. The 
gneiss on the eastern declivity of the mountain, for some distance from the crest, is horn¬ 
blendic, and the dip is to the eastward where it is not vertical. 
The heavy swell of land, composed in part of talcy slate, east of the limestone that was 
seen near Bonnell’s forge, is bounded on the east by Horton’s pond and its outlet. Gneiss 
was frequently seen in place after passing into the valley of the pond; and on the eastern 
side of its outlet, the rock had much the aspect and composition of some of the felspathic 
and sienitic rocks southeast of Peekskill, though they had more of a granitic aspect. 
The rocks at Coldspring landing are gneiss, hornblendic gneiss, and granite. The strata 
have.a north-northeast and south-southwest direction, and the dip is vertical at the south 
point. 
Constitution island, between Coldspring and West-Point, is composed of gneiss, hornblen¬ 
dic gneiss, granite and sienite. The stratification is much confused, and some of the rocks 
have a strike transverse to the usual direction, viz. northwest and southeast. This appears 
to be on the transverse line of disturbance that has been observed farther east-southeast in 
several places, and on the west-northwest near the cascade, and on the mountain farther west. 
Granite and sienite form the Target rock, a high cliff on the southwest side of the island, and 
granite forms some of the points farther north. Hornblendic rocks (gneissoid) form the shore 
a little north of the Target rock ; they lie in strata dipping at high angles to the northeast, 
and some are nearly vertical. 
The rock at the Floating dock at the steamboat landing at West-Point is granite, as also 
Gee’s Point. Granite is seen in abundance on the sloping ridges, leading from the plain of 
West-Point north towards the Hudson, between Kosciuszko’s monument and the Cadet’s 
monument; these are distant from each other 416H feet.* 
Flat rock at Mr. Arden’s boat landing, two and a half miles south of West-Point, is 
granite. 
The geological explorer can scarcely fail of finding numerous localities of granite, gneiss, 
sienite, greenstone, hornblende rock, augite, limestone, etc. in exploring the shores of the 
Hudson through the Highlands. 
* The maps of the Highlands are extremely inaccurate, so that they are of little aid in fixing localities. With a view 
of noting down alt the facts connected with the complicated geology of the Highlands, I began a triangulation of the 
country for several miles around West-Point, and prosecuted it when not otherwise engaged in 1833 and 1834. Some 
progress had been made in the construction of a topographical map of that region, based on triangulation, as accurate as 
I could effect by a common theodoUte, and measurement of a base line with the common measuring tape. The map, as 
far as constructed, has been lost; but some of the notes and results ol the calculation of the triangles remain, and they 
are subjoined, as they may aid some one in the construction of a map. The original base line or line of reference is a 
prolongation of the north end of the North Barrack at West-Point; 4ts western extremity being 414^ feet westwardly 
from the northwest corner of that building, on the line mentioned ; and the eastern extremity is on the edge of the plain 
on'the above line eastwardly from the barrack. The whole length of the base line is 1036^ feet. 
