DAKTON.] 
NEW YORK. 
23 
LONG ISLAND. 
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GENERAL GEOLOGIC RELATIONS. 
Long Island consists of a great mass of glacial drift lying on Creta- 
ceous and probably also Tertiary formations. The Cretaceous forma- 
tions lie on a floor of crystalline rocks, which is deeply buried to the 
south, but rises gradually to the north and emerges at the surface in 
Long Island Sound, in Connecticut, and 
on the northwestern corner of Long 
Island. The Cretaceous formations, and 
probably also the Tertiary, are a succes- 
sion of widely extended sheets of sands, 
clays, etc., which are often considerably 
flexed locally, but as a whole dip to the 
south or south -southeast. They also 
probably thicken and increase in num- 
ber in the same direction. The drift 
comprises the great terminal moraine of 
the Second Glacial Epoch, which rises in 
a range of high hills extending along 
the center of the island, and a variety of 
Pleistocene dejiosits of which the rela- 
tions have not yet been fully determined. 
It consists mainly of mixtures of sands, 
pebbles, and bowlders, and beds of sand, 
clay, and sandy clays, presenting con- 
siderable complexity of structure. It 
lies on an irregular, deeply eroded sur- 
face of the older formations, but the 
contour of this surface is not determined 
over a wide area. 
The following cross section of Long 
Island shows the general relations and 
also indicates the position and features 
of some of the wells. 
WELLS OF LONG ISLAND. 
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The artesian water supplies of Brook, 
lyn are of world-wide fame, for their 
amount is phenomenally large and the 
quality of the water is exceedingly good. 
The wells are of moderate depth — 100 to 150 feet — and the waters do 
not come from any definite geologic horizon, but are simply accumu- 
lations in or under the drift deposits in localities where the physical 
conditions are favorable. There are other wells at various points 
on the island which, in the main, obtain satisfactory water supplies, 
