a
shaft 147 feet deep. And recent borings for water, conducted by the
Arbuckle Brothers at Jay Street and in the block bounded by Pearl,
John, Plymouth, and Adams Streets, have still further conclusively
shown this. Over 2,000 feet of solid rock was penetrated in this
unavailing search, which resulted in an impoverished supply of saline
water. It has further been demonstrated that generally under Long
Island this supporting arch is reached at varying depths: at Wood-side,
for instance, the rock is 500 feet below the surface, at Greenport it
is 650 feet deep, and at the northern point of Great Neck 325 feet, and
on the west from Bay Ridge to Bath Beach it is 200, 300, 400, 500 feet,
progressively.
The
entire superstructure of the land over these basal beds is not,
however, entirely drift. Conclusions previously held by inference have
in late years rapidly culminated into proof that a widely extended
group of clay beds referable to the Cretaceous, and possibly Tertiary
formations, underlies Brooklyn and Queens or, indeed, all Long Island,
and on these rise the great morainal piles which are yet well
characterized in undisturbed perfection within the limits of Brooklyn
city. These latter are reviewed in the following section on glacial
geology.
As
long ago as 1838 Mather, of the New York State Survey, observed the
resemblance of clay beds on the north of Long Island to the clays of
the Raritan beds of New Jersey, and this caused him tentatively to
assign to both a geological equivalence. And now this cretaceous sheet
has been traced eastward into Martha's Vineyard, and our imagination is
permitted to reinvest this coastal area with tropical vegetation at
that long distant day. This topic of the geology of Long Island
solicits introduction at this point in this book, and sensibly becomes
urgent by reason of inquiries by school-teachers as to this very
subject. It has also secured an authoritative presentation in the
Professional Paper, No. 44, of the United States Geological Survey.
(Veatch, Slichter, Bowman, Crosby, and Horton.)
