184 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
emerge at the surface and are exposed in railroad cuts, etc. The floor 
of crystalline rocks rises to the surface west of the railroad. 
PRINCE WILLIAM COUNTY. 
The conditions in this county are precisely similar to those in Fairfax 
County. The Potomac formation occupies a belt extending about 3 
miles west from the river, but the distance is less in the larger depres- 
sions. The well at Barrow on the Potomac developed a large water 
supply at a depth of 143 feet in Potomac beds, and it is probable that 
another water horizon would have been found in the basal beds lying 
on the crystalline rocks from 150 to 200 feet below. 
STAFFORD COUNTY. 
The conditions in Stafford County are similar to those above described, 
but the area underlain by the Potomac formation widens rapidly south 
ot the Potomac Creek. The well at Quantico found water in the basal 
Potomac beds at 210 feet, and there is every reason to believe that this 
water extends over the entire area occupied by the formation. Along 
the eastern border of the county, south of Aquia Creek, there is a belt 
of country about 3 miles wide in which the basal Pamunkey gravels 
will be found to contain water at depths which increase to about 75 
feet below tidewater level along the King George line. The basal 
Potomac waters are at least 400 feet deeper, but there is everywhere a 
fair prospect for water at higher horizons within the Potomac formation. 
KING GEORGE COUNTY. 
Although I know of no deep wells in this county, the geologic condi- 
tions and the indications of the Colonial Beach and Chapel Point (Md.) 
wells are such that water may be quite safely predicted throughout the 
county in the basal Pamunkey beds. The depths will be found to 
increase gradually from about 75 feet below tide- water level along the 
Stafford line to 200 feet on the Westmoreland line. Waters may also be 
expected at greater depths in the Potomac sands. Some of the rela- 
tions of the beds in the county are shown in sections 1 and 2 of PI. XVI. 
WESTMORELAND COUNTY. 
This county is underlain throughout by the Pamunkey horizon at 
depths which increase from 250 feet at Colonial Beach to 386 feet at 
Naylors Wharf. At greater depths the Potomac waters may also be 
looked for, but there is less certainty of these lower waters eastward. 
The eastern part of the county is also underlain by the basal Chesapeake 
waters, which lie about 250 feet higher than the basal Pamunkey hori- 
zon. They have been extensively developed in the flowing wells from 
Coles Point, where their depth is 220 feet, to Kinsale and Sandy Point, 
where they are 235 feet below tide-level. 
