136 
GEOLOGY OF THE FIRST DISTRICT. 
composed of coarse gravel, pebbles and boulders. These seem to have been transported by 
a stronger current rushing from the north through the channels that will be named, to the 
localities where they are now found. 
In the subjoined quotation from Prof. Gale’s report to me on the Geology of New-York 
island, it may be understood that the diluvium mentioned by him, in many localities, refers 
to these upper drift beds overlying the proper quaternary sands and clays. 
“ The island contains in every part abundant evidence of a current having swept over it 
from northwest to southeast, both from the grooves and scratches* still visible on the solid 
rocks of the island itself and its vicinity, and from the materials themselves being traceable to 
the original rocks whence they have been transported. Tlie southern part of the island con¬ 
tains the largest amount of these materials. In the southeastern extremity of it, usually de¬ 
nominated Corlear’s hook, the surface has been graded in some places seventy or even eighty 
feet below the natural level, and shafts have been sunk seventy-five or eighty feet more with-, 
out reaching the rock. The diluvium and alluvium together are therefore in this vicinity at 
least one hundred and fifty feet, the streets having been graded in some places half that depth 
below the original soil. It is proper to state that the whole of Corlear’s hook and its vicinity 
originally consisted of a series of conical hills of diluvial sand, gravel and pebbles, with 
masses of all sizes, from pebbles to boulders fifteen or twenty feet in diameter ; all of which 
have been removed and deposited in the neighboring valleys and low grounds. Here were 
collected, not only the largest quantity, but the greatest variety of rocks that were found in 
any part of the island. 
“We will now enumerate the different depths at which the rock has been reached by 
borings for water, or for other purposes, in different parts of the island which are covered by 
alluvium or diluvium. Most of these borings were commenced in this city many years ago 
by Mr. Levi Disbrow ; and the same business is successfully conducted by his son, Mr. John 
Disbrow, from whom most of the subjoined facts were obtained. 
“ Commencing at Corlear’s hook, we find a shaft was sunk at Mr. James P. Allaire’s works, 
in Cherry-street, about eighty feet through diluvium, stratified sands, clays, or gravel, with¬ 
out reaching the rock. Again to the westward about half a mile, at the foot of Jefferson- 
street, the rock was reached through ten feet of diluvium, and forty feet of stratified sands, 
and'gravel alternating with clays. 
“ At Fulton market, a shaft was sunk through fifteen feet of artificial ground; then one 
hundred and fifteen feet of stratified sands, blue clay and river mud alternating, and the rock 
was struck at the depth of one hundred and thirty feet. 
“ At Holt’s hotel, a few rods north of the last mentioned place, a shaft was sunk through 
one hundred and twenty-six feet of strata like those at the market, and the rock reached 
through a bed of gravel, and the shaft sunk five hundred feet into the rock, which is gneiss 
* The grooves and scratches are believed to be principally due to the action of the lower drift deposits, lying below the quater¬ 
nary sand, gravel and clay beds, and which are frequently partially cemented by clay into what is often called “ hardpan.” This 
will be discussed under Drift. 
