18 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
report would in a measure meet the great demand, that exists for infor- 
mation as to well prospects and the general relations of the water 
horizons. 
Notwithstanding the fairly large number of wells, the information 
is meager for many portions of the region. Few of the well records in 
the southern portion of the area and on Long Island are sufficiently 
definite to fully indicate the geologic relations of the water horizons 
and their associates, but some general features are quite clearly indi- 
cated. In New Jersey, Maryland, and Virginia there are many wells, 
and the geology is so relatively plain that it has been possible to defi- 
nitely determine the position of many of the water-bearing horizons 
and to predict water almost everywhere with a fair degree of certainty. 
GENEKAL GEOLOGIC STRUCTURE OF THE ATLANTIC 
COASTAL PLAIN REGION. 
It is proposed to give under this heading a brief outline of the gen- 
eral geologic features of the region in order that the relations of the 
water-bearing strata may be clearly understood. More detailed descrip- 
tions of local features will be given in subsequent chapters. 
The Coastal Plain is a geographic province which extends along the 
COASTAL PLAIN 
Fig. 1.— Section across the Atlantic Coastal Plain from west* to east. 
eastern margin of the Atlantic Slope from Long Island to Florida. Its 
width averages about 100 miles, exclusive of a submerged seaward 
extension out under the Atlantic Ocean. The surface is in greater 
part smooth or gently rolling, and westward it slopes up gradually to 
altitudes of from 300 to 400 feet in the Northern States and to heights 
somewhat greater toward the south. It is deeply intersected by bays 
and long, narrow tidal estuaries of rivers, which are surrounded by 
low lands near the ocean, but are flanked by moderately high plateaus 
and hills as the country rises inland. 
The region is underlain by a series of great sheets of unconsolidated 
deposits, consisting mainly of sands, clays, and marls, which lie on an 
east-sloping floor of older rocks, predominantly granite and gneiss. 
These deposits constitute a great flat wedge, inclined to the east and 
southeast, and presenting its thin edge to the west and northwest. 
The underlying rocks emerge at the surface along a line which passes 
from New York city through Philadelphia, Baltimore, Washington^ 
