SUEVEY OF THE ISLAND OF NEW-YORK. 591 
67th to 66th-street: On the west side gneiss unfit for working ; grooves abundant. Direc¬ 
tion N 46° W. Dip vertical, and strike N 30° E. 
66th to 64th-street: Gneiss like last, and covered with abundance of grooves in good pre¬ 
servation. Rock but recently uncovered; is fast disintegrating. Grooves on both sides of 
the road. Direction N 45° W. Strike N 35° E. 
The whole distance from Harlem and Manhattanville valley to the Bloomingdale road, or 
about 62d-street, on the line of 8th avenue, is extremely rough and rocky. The gneiss is 
abundantly charged with veins of granite towards the southern portion of the route, while 
there is little of it in the northern. The grooves are more abundant, and perhaps more dis¬ 
tinct, taken as a whole, than I have seen in any part of the island, and should be reexamined 
for taking drawings of some of the most remarkable. 
Seventh, Sixth and Fifth Avenues. 
The above avenues, except the 6th, are only opened to a short distance (21st-street); and 
as the ground in most of the surfaces is occupied by these streets, it is similar in character. 
The remarks on one will generally apply to all. 
7th avenue commences at the corner of Greenwich lane and Hammond-street. Surfaces 
composed of loam, gravel and pebbles : here and there a house. The same geological cha¬ 
racter continues to 21st-street, where the opening terminates, 
24th-street: The rock, which is gneiss, with large veins of sandy granite. Strike N 20° 
E. Dip 45° to 50° W, covered in many places with fine yellow sand. 
6th avenue commences at Carmine, near 4th-street, and terminates at Bloomingdale road, 
at 32d-street, where gneiss has strike N 20° E. Dip 80° W. Not tortuous, but ferruginous. 
29th-street: Gneiss makes its appearance. Strike N 15° E. Dip W 80°, Generally 
sound, and full of quartz veins. 
Corner of 6th avenue and 20th-street, gneiss. Strike N 30° E. Dip 75° W. 
At 17th and 18th-streets : Have dug twenty feet through ; first six feet gravel, then fourteen 
feet fine sand, and at the bottom came to a dark-blue clay, containing vegetable matter in a 
state like lignite. 
5th avenue, corner of 16th-street, and along 16th-street each way, the gneiss within four 
feet of grading. Strike N 30° E. Dip 75° W. Strata generally regular. 
5th avenue, at 33d-street, gneiss abounding in granite veins, somewhat tortuous. Strike 
N 20° E, three places. Dip W 80°. The veins contain large imbedded crystals of felspar ; 
veins have protruded and disturbed the stratification. The rock, though exposed, has drift 
grooves obscured by exposure, but six inches wide and one and a half deep, running north 
25° west. 
