No. 275.J 
179 
3. General remarks on the transported materials of the island, both al- 
luvial and diluviaL 
4. Alluvial beds or valleys. 
6. Boulders^ their abundance and sources in different sections. 
6. Minerals enumerated. 1st. Those peculiar to the rock of the islands 
2d. Those that have been transported, 
7o, Diluvial grooves and scratches. 
i. 
Descripiio7i of the region between the city of Mew- York and ike Hariem 
and Manhattanville valley. 
The section lying between the settled portion of the city and the 
level valley extending from Manhattanville on the Hudson, to Harlem 
on the East river, is generally bounded on the south by the out-crop- 
ping of the gneiss, which as before stated, commences on the west at 
31st-street on the 10th avenue, and at 29th-street on the 9th avenue, 
at 28th-street on the 8th avenue, at 24th-street on the 7th avenue, at 
20rh-street on the 6th avenue, and at 16th- street on the 5th avenue, 
where it comes within 4 feet of grading; on ISth-street, between Uni- 
versity place and Broadway, it again approaches within three feet of the 
surface- and on 4th, 3d and 2d avenues, at their several junctions with 
16th-street, it appears at or above the surface; while on the 1st ave- 
nue, it crops out first at 21st-street, and continues as we progress to 
the northward on the banks of the East river, until we reach 94th- 
Street, which is at the eastern termination of Harlem flats, where the 
rock dips below the surface, leaving a salt marsh which from this point 
continues northward. Again commencing on the west side of the island, 
w^e find the rock continues from 31st-street northward to Manhattan- 
ville, almost constantly above the surface at or near the water's edge. 
The elevated points of this section of the island vary from 70 to 120 
feet above tide water mark, and will when graded, give at a rough esti- 
mate a medium level of about 40 feet above the contiguous waters. 
The valleys, however, are often deep, and the hills precipitous, render- 
ing this section rough and broken. 
The 3d^ 4th and 8th avenues have been cut through until they reach 
the Harlem river; the first two terminate at Harlem, the other at Mc- 
Cornb's dam; 5th and 7th avenues terminate at 21st-street; 6th ave- 
nue extends to the Bloomingdale road at 32d-street; 10th avenue to 
the same road at 70th-street, in the village of Bloomingdale; and 9th 
avenue terminates at 42d-street. 
