SURVEY OF THE ISLAND OF NEW-YORK. 
587 
15th-treet, and west side of avenue are numerous boulders in the open grounds. Some 
eight or ten of these are of the dark ferruginous anthophyllite, and are from three to eight 
feet diameter, much worn, and very smooth on those faces which resist decomposition by the 
weather. 
15th to 16th-street: Open grounds ; most of it is made land, and where natural soil, it is 
sand and gravel. 
28th-street; Gneiss appears above the surface, with veins of granite. Strike N 30° E. 
Dip W 80° to 85°, and disappears a few rods north. 
28th to 30th-street: Alternations of sands and pebbles, containing largely granite, green¬ 
stone and sandstone fragments of all sizes. 
36th-street: East side the rock is gneiss and granite, a fair workable material for co mm on 
work, and much may be got out for facings. Strike N 10° E. Dip W 85° to 90°. 
38th-street: Granite and gneiss ; a quarry east side of avenue, twelve to fifteen feet deep? 
not wrought at present; somewhat tortuous. Strike N 8° to 10° E. Dip 85° W. Twenty- 
five rods further east gneiss again. Strike north and south. Dip 75° west. Apparently fair 
rocks for diluvial grooves, but none were observed from 38th-street to 40th-street. 
41st to 42d-street: The rock is a coarse granite, but very sound, six to ten feet above 
grading; in sight one hundred and seventy-five feet east and west, and four hundred and ten 
feet north and south. 
Northward from 42d to 49th-street, the grounds are pretty level. 
50th-street: The rock is gneiss, highly stratified and fissile. Strike N 20° E. Dip 80° 
to 85° W. On the east side are boulders of anthophyllite of the dark ferruginous kind. 
54th to 55th-street: Gneiss appears ten feet above the surface, and has the strike N 30° 
E. Dip W 60°. Well stratified, not tortuous or containing veins. 
58th-street: The gneiss is twelve feet above the surface of grading, and strike N 30° E. 
Dip vertical. Drift furrows east side of avenue, and west of the Bloomingdale road, and 
within a few rods of the junction. 
Near the junction of the road and avenue, but towards the northwest of it, and at the dis¬ 
tance of say one hundred yards, the gneiss has been worn down to great depth by the 
materials that have travelled over it; grooves are distinct, and wonderfully so for a diameter 
of two hundred or three hundred feet, in every direction, all in fair view of the road, and on 
the northeast side the grooves cover almost the whole rock, but are most apparent on the 
west side ; and this last remark applies equally well to all the grooves on the island. Direc¬ 
tion of the grooves N 45° W. Strike N 30° E. Dip vertical. This rock contains veins of 
fine granite, one to ten feet wide, and the part recently uncovered has been worn completely 
smooth. Other grooves are seen near the Bloomingdale church. Direction N 45° W. 
Again farther north near Mr. Huddart’s school, on the same road, west side. Direction N 
45° W. 
Again twelve to fifteen rods north of Burnham’s hotel are grooves very finely characterized. 
Direction N 45° W. They are on the east side of the road. 
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