WATER RESOURCES. 359

quality and suitable for most ordinary purposes. Elsewhere the
amount is excessive and the waters are unpalatable and not satisfac-
tory for either domestic or manufacturing purposes. Iron salts are
present in many cases and, in the case of some wells, in excessive
amounts. The odor of hydrogen sulphide may be detected in many of
the waters when they first issue from the wells. Flowing wells have
been obtained at many places, as a rule, on ground lower than the gen-
eral level of the region immediately surrounding the wells.

The water conditions of the several counties in the area under con-
sideration have been treated separately elsewhere in’ this report.

The area over which potable waters may be obtained from the

Miocene and marine Pliocene formations by drilling is indicated on
the map (Plate XXXVI).

TERTIARY AND QUATERNARY.

SURFICIAL PLIOCENE? (LAFAYETTE FORMATION) AND PLEISTOCENE.

The Lafayette and Pleistocene deposits, because of their lithologic
similarity and because both exist as surficial coverings upon older for-
mations, may be appropriately treated under one heading. From the
standpoint of the actual, practical use to which they have been put in
the past, and the use, though constantly diminishing, to which they are
still being put, these formations may be regarded as the most important
of all the Coastal Plain aquifers in the State. Their availability as a
source of supply, however, is so well known, and the means of obtain-
ing the water are so simple and easily applied that there is little need
of treating them exhaustively here.

The Lafayette deposits are present as, surficial coverings, probably at
but few places exceeding 25 or 30 feet in thickness, along the north-
western border of the Coastal Plain province. (See geologic map, Plate
XIII, in pocket.) They rest in part upon ancient rocks, and in part
upon beds of the Patuxent formation. They occur for the most part
at elevations of from 200 to 500 feet and form mantle-like coverings
which cap the tops of, and lap down over the slopes of, the pre-Lafayette
hills. The sandhill country in the southwestern part of the Coastal
Plain region forms a part of this area. The materials consist of sandy
loams and sands, as a rule coarse and -in places arkosic, and having at
their base at many places a bed of coarse gravels and cobbles. Except
very locally, they are loose in texture and permit of the free passage of
water among their constituent parts. Where the materials on which
the Lafayette deposits rest are more compact and less pervious to water
than the Lafayette materials themselves, the basal beds of the latter