WATER RESOURCES, 851

the valley of Contentnea Creek northward the Patuxent (“Cape Fear”)
beds lie beneath superimposed Miocene beds which must first be pene-
trated when seeking to obtain water from horizons in the former.

The area over’ which it is believed possible to obtain potable water
from the beds of this formation by means of borings is shown on the
map, Plate XXXII. It includes not only the belt of outcrop of the
formation, but also an additional strip lying to the southeast of this
belt, where it is possible to reach the beds by boring through the over-
lying younger deposits. It is probable that the Patuxent (“Cape Fear’’)
formation extends farther coastward than the limit indicated on the
map, but it is believed that beyond this limit the deeply buried waters
are highly mineralized and undesirable for ordinary domestic and man-
ufacturing purposes.

The materials of the Patuxent (“Cape Fear”) formation consist of
layers and lenses of light-gray, arkosic, more or less micaceous sands and
light to dark drab, more or less arenaceous clays. Both the sands and
clays are in many places very solid and compact and in places the sand
layers are indurated to form solid rock. In the case of the sand the
compactness seems to be due in the main to a filling between the grains
of very fine kaolin or clay particles. However, open porous layers
occur, and this is more especially true along the northwestern part of
the area where the materials are in close proximity to the basement
rocks from which they were derived. The materials here are coarser
as a rule, also, than is true of those farther away from the Piedmont
border. It is believed, also, that the buried basal portion of the forma-
tion where it rests upon the older rocks consists largely of coarse sands
and gravels.

The thickness of the formation, so far as known, appears to be
about 300 feet. It may become somewhat thicker, however, for a short
distance to the southeast of its belt of outerop.

Experience has shown that. water-bearing beds occur within this for-
mation. The water, of course, circulates more freely in the more
porous beds. These may occur at any vertical position within the for-
mation. Owing to the irregularly varying porosity of the different
beds it is impossible to predict from surface indications at any given
locality at what depth those will be encountered which are sufficiently
porous to admit of free circulation of water; but since the beds nearer —
the base are believed to be in general more porous than those occupying
a higher position, it would seem that these would offer the more promis-
ing horizons; and in places at least, which can only be determined by
drilling, they should furnish very large supplies. The depths at which
potable waters should be found in this formation. will vary all the way