36 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
experience of this well adds important confirmatory evidence that 
fresh- water supplies may be expected far below the bottom of Long 
Island Sound on the north shore of the island. 
WATER HORIZONS AND WELL PROSPECTS ON LONG ISLAND. 
Our knowledge of the underground geology of the island is not yet 
sufficiently far advanced for a discussion of water horizons, and no safe 
basis for well prognostication can be established until the geology is 
understood. Owing to the peculiar geologic structure of Long Island, 
with its great accumulations of heterogeneous glacial drift, we can not 
infer the underground structure from studies on the surface, and our 
data must come mainly from careful records of wells. As the records 
are so few and most of the wells so shallow the data now available are 
too meager to throw much light on the subject. In the opening remarks 
of this chapter I explained the general underground structure and 
showed how the south-sloping floor of crystalline rocks was overlain by 
a series of. sheets of sands, clays, etc., which, as a whole, are thought 
to dip gently to the southward. It is believed that there are beds and 
streaks of coarse sand and gravels in this series which carry water, and 
1 have considerable confidence that they will yield water to deep wells 
in wide areas on Long Island. They outcrop along the shores of the 
sound, and, as is shown in the cross section, lie quite far below the sur- 
face along the south shore. They proved to be fine grained and appar- 
ently nonwater-bearing in the Woodhaven well, and there is possibility 
that this condition exists in other areas, but the prospects for water in 
these lower beds is, I believe, sufficiently promising to warrant the sink- 
ing of other wells to the basal beds. The depth to these beds along 
the south side of the island is about 1,000 feet, and they rise gradually 
to the northward so as to emerge at the surface along or near the north 
shore. On the eastern end of the island they appear to lie somewhat 
deeper than they do to the west, where the underlying crystalline rocks 
emerge in the Long Island City region. Precise figures can not be 
given, for no wells have been sunk to the crystalline rocks east of 
Woodhaven, and we can only assume that the rate of slope is as uni- 
form eastward as it is known to be in the region westward. 
It is thought that the wells on Sands Point and Bowery Bay, and 
probably other deep wells along the north shore, find their waters in 
beds not tar above the basal sands, etc., which lie on the bed-rock floor. 
The higher horizons on Long Island appear to be in the drift and 
associated with clay beds of which the relations and distribution have 
not yet been ascertained. In the vicinity of Jamaica and southward 
the deeper waters of the Brooklyn city supply are from under a clay 
bed which appears to underlie an area of considerable extent. 
During the past year these waters have been extensively explored 
by test wells by the Brooklyn City Water Department, and found to 
be available for large water supplies. These explorations have also 
