QUATERNARY DIVISION. 
139 
beds bordering on the valley as that drained from the surface of higher grounds; Avhile that 
from lower strata, as from the black mud above mentioned, was derived from the river either 
directly or indirectly, and being heavier, retained its place at the bottom. 
“ The second alluvial valley lies on the east side of the island, and includes what was for¬ 
merly called the Stuyvesant meadows, and all the low ground extending southward to the 
vicinity of Corlear’s hook, or from Twenty-first-street on the north to Delancy-street on the 
south, and from the river on the east to about half a mile westward ; this last boundary vary¬ 
ing somewhat in its distance from the river in different portions of it. This region is throughout 
a salt marsh, and was formerly to a considerable extent covered by the tide at every flow, but 
is now shut out by dykes and filling in of the streets. The strata composing this alluvion are 
mostly alternations of sands, clays and mud, and beds of sand or gravel resting on the rock, 
which last is from ninety to one hundred feet below the grade level surface. 
“ The following are some of the results of borings made in this alluvial district. At the 
corner of Fifth-street and Avenue D, a shaft was sunk, which reached the rock at the depth 
of one hundred and nine feet. 
“ At the Dry Dock another was sunk, which came in contact with the rock at the depth of 
one hundred and thirty feet, and penetrated it two hundred feet, 
“ At the corner of Houston and Lewis-streets, the rock was reached at ninety-four feet. 
At the corner of Houston and Avenue D, at ninety-six feet, and at the corner of Seventh and 
Lewis-streets, the rock was reached at ninety-three feet; and at the corner of Seventh-street 
and Avenue D, it was reached at the depth of one hundred feet. In these borings, it is evi¬ 
dent that the rock dips down on the east side of the island to about one hundred feet below 
the grade level of the streets, 
“ The third bed of alluvium is that already referred to under the name of the Harlem and 
Manhattanville valley ; the form of which approaches that of a scalene triangle, having the 
longest side on its southern borders, and extending from the village of Manhattanville on the 
Hudson to the termination of Ninety-fourth-street on the East river; its shortest side from 
Manhattanville to the northern limit of Harlem village, near One-hundred-and-thirtieth-street; 
and the remaining side from the last named point on the north, to the termination of Ninety- 
fourth-street on the south. The width of the island at this place is about two and a half 
miles, and the length of the valley east and west the same, while its extent north and south 
is about two miles. The strata throughout the valley are alternations of sands, loam and 
gravel, generally in strata, but sometimes in conical hills thrown together in great confusion; 
and when this is the case, it is gravel and pebbles rather than sand or loam. The gravel and 
pebbles predominate towards the western portion of the valley ; sand and loam in the eastern. 
Boulders are less abundant in this than in most other portions of the island. 
“ Comparatively few excavations or borings have been made in this valley ; consequently 
we have fewer data for determining the depth of earth covering the rock. In the northern 
part of Harlem village, at the corner of Fourth avenue and One-hundred-and-twenty-ninth- 
street, the rock appears, and has been removed by blasting ; and in a number of other places 
in the vicinity, it approaches the surface or within a few feet of it. Indeed it is inferred that 
