PRIMARY ROCKS, 
517 
to six thousand feet. These counties present one of the finest fields in our country for the 
investigations of physical geology. A lifetime might be well spent, and with advantage to the 
community from its economical results alone, in developing the geology of the Primary region. 
Numerous details on this region are omitted, as a volume would be required to elucidate the 
facts. 
The Highlands in Rockland and Orange are a continuation of those of Putnam and 
Westchester counties, and are similar in general aspect, in the kinds of rocks, and in their 
mineral products. The rocks consist of gneiss, and hornblendic gneiss, granite, sienite, lime¬ 
stone, hornblende, serpentine, augite and trappean rocks. The strata dip to the southeast at 
angles from fifty to ninety degrees, but there are localities where the strike and dip are trans¬ 
verse to the general directions. The strata are intersected by seams transverse to the direc¬ 
tion of the strata, and nearly perpendicular to the line of bearing, and at intervals of one 
hundred to ten thousand yards. Dislocations and vertical and lateral heaves have occurred 
along many of these lines of fracture. The outcropping edges of the strata are not parallel 
to the line of bearing, but like the ridges slope gradually down to the northeast; while on the 
southwest, steep escarpments range along the lines of faults. Many of these faults are upon 
an enormous scale, and render the tracing of narrow beds of rock of economical value a 
matter of no small difficulty. There are no continuous ridges of mountains of more than a 
few miles in length, in consequence of the interruptions caused by dislocations and lateral 
heaves of masses of the strata. The hills of similar rocks succeed each other in echelon 
lines, which seem to have been caused by lateral heaves along the lines of fault. In conse¬ 
quence of this, neither the line of outcrop nor the line of bearing is parallel to the general 
direction of the Highlands, but ridge succeeds ridge, each of which runs out and diminishes 
in height until it disappears below the rocks which are generally considered of more recent 
origin. 
In Washington and Saratoga counties, the direction in which the ridges slope down and 
disappear is in the reverse direction from that in the south part of the State. In the southeast 
part of the State, the ridges present cliffs at their southern ends, and slope down gradually 
to the north, until they disappear and are succeeded by others; while in the north part of the 
First district, the ridges show cliffs and steep escarpments on their north ends, and slope 
gradually down towards the south until they disappear. 
Local Details, . 
On Staten island, Richmond county, the rocks included in those now under consideration 
were seen in only one locality. The rock was granite, and was seen, on the shore opposite 
Nautilus Hall, at the Quarantine. It is coarse grained, composed of white and smoky quartz, 
red and grey felspar, and mica. It is seen only over a space of a few square rods, and is 
covered by the deposits belonging to the erratic block group. It is not of a suitable texture 
for a building material, and cannot be applied to any useful purpose, except as a rough wall 
stone. 
