86 
[Assembly 
from this quarry to be used in the construction of the culverts and bridges 
f the aqueduct that leads from the Croton river to supply New-York 
city with water. 
Numerous other quarries have been opened along the line of the aque- 
duct, in the bed of gneiss just spoken of, and in others, to supply stone 
for this great work. It is not doubted that several of these quarries 
which lie near water transport, will be wrought for the New-York and 
other markets. Our citizens do not yet appreciate the prospective value 
of good quarries on the banks of the Hudson river. 
Another range of gneiss, suitable in many places for quarrying, ex- 
tends from near Manhattanville, on New- York island, by White Plains 
and so on NNE, probably into Connecticut, or Putnam county. It en- 
teisthe valley of the Bronx river about eight or nine miles below White 
Plains, while it forms a part of the range of hills on the right bank of 
that, for several miles below. 
At one locality in this range, the rock is quarried to some extent, to 
furnish the stone for the aqueduct bridge across Mill river, near Yonkers 
or Philipsburg. It is an excellent, beautiful stone, but rather hard to 
dress. This stone will last as long as it will be required to endure, and 
it seems indestructible. 
A gneiss quarry has been opened two miles east of Yonkers, on the 
land of Elijah Valentine. The rock is of a superior quality, and is used 
in the construction of arches in the aqueduct. The proprietor receives 
a rent of 12h cents per cubic yard for the stone. 
The facts of scientific interest connected with the gneiss ranges, will 
be retained until the final report. 
III. MICA SLATE. 
This rock has a very limited distribution in New- York, Westchester 
and Putnam counties. Where it does occur, it seems to be a modifica- 
tion of gneiss, the mica becoming predominant, while within a short 
distance, the rock resumes its characters of gneiss. No locality was 
observed where there is prospect of valuable quarries of flagging stone, 
of this kind of rock being opened, near water transport. A locality of 
mica slate, well characterized and fissile, may be seen, forming a point 
in Haverstraw bay, half to one mile northwestwardly, from Henry I. 
Cruger's mansion. This rock assumes the characters of gneiss, two or 
three miles NNE of the point above referred to, and thence continues 
its course in the line of bearing of the strata. 
