188 
[ASSEMBLT 
This first valley being a fresh water alluvion, and a quagmire origi- 
nally, was of great depth, as has been recently proved by soundings 
made by Mr. Disbrow, in the place now occupied by the Halls of Justice 
in Centre-street, between Franklin and Leonard-streets, where iron rods 
were sunk 40 feet through artificial earth, 30 feet through black mud, 
5 to 10 feet of blue clay, then a bed of gravel resting on the rock. Still 
farther south, at the Manhattan water works, on Centre, between Reade 
and Duane-streets, seven shafts were sunk 30 feet each in coarse diluvi- 
al gravel without reaching the rock. The water supplied by the Man- 
hattan company is by no means the best in quality, but is used for want 
of better in culinary operations in a considerable portion of the southern 
part of the city. 
The black mud brought up from the lower part of the strata of the 
Collect was as salt as the waters of the river, though very good water 
was obtained at a higher level on the outskirts of this valley. This fact 
is generally explained by considering the water from the gravel beds 
bordering on the valley as that drained from the surface of higher 
grounds; while 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 in- 
cludes what was formerly called the Stuyvesant meadows, and all the 
low ground ►extending southward to the vicinity of Corlear's hook, or 
from 21st 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 
varying somewhat in its distance from the river in different portions of 
it. This region is throughout a salt marsh, and was formerly to a con- 
siderable 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 allu- 
vion are mostly alternations of sands, clays and mud, and beds of sand 
or gravel resting on the rock, which last is from 90 to 100 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 109 feet. 
At the Dry Dock another was sunk, which came in contact with the 
rock at the depth of 130 feet, and penetrated it 200 feet. 
At the corner of Houston and Lewis-streets the rock was reached at 
94 feet. At the corner of Houston and Avenue D, at 96 feet, and at 
