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wells enough water is found in the first bed while in others it is necessary to go slightly deeper. This condition is due to the fact that the materials in the lower part of the Calvert are rather variable and for this reason water may be forced down slightly by a change in lithology.

The Calvert water is reported to be soft and an analysis of water from Millstone made on the grains-per-gallon system is given by Shattuck and Miller' in the St. Mary's folio. This analysis is not very complete, but shows rather large amounts of calcium, magnesium, and sodium carbonates with the alumina and iron oxide combined as .0525 grain per gallon. The alumina probably comprises almost all of this amount, since iron is not present in large quantities in the Calvert water. The analysis is given below.

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The Eocene water in this county comes from a level that at Chaptico and west of Maddox is about 90 feet above the water at the base of the Aquia. As shown by the sections given below, which have been taken from the drillers' records at these places, the water comes from a bed in the uppermost Aquia trapped under the lowermost bed of the Nanjemoy formation.

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1 Geologic Atlas, U. S. Geological Survey, St. Mary's folio No. 136, p. 7, 1906.

WELL AT CHAPTICO

Feet

Light-yellow sand, containing small white quartz pebbles..
Dark-gray sand with shell fragments....
Gray sand with many shell fragments..

1-20

20-70

70-80

Gray sand with a few shell fragments...

80-120

Light-gray sand with many glauconitic grains...

.120-250

Dense yellow clay, glauconite grains probably from beds..
Yellow sand with many glauconite grains....

250-270

270-295

Stratigraphically this water is not Nanjemoy but comes from the upper part of the Aquia formation, but since in the literature the position has always been given as the base of the Nanjemoy and there is another waterbearing level in the Aquia formation, this water horizon may still be called Nanjemoy to avoid confusion.

Numerous wells in the northwestern part of the county at Oakley, Palmers, Portobello, Bushwood, Compton, and on Blakistone Island, besides those at Chaptico and Maddox, draw from this Nanjemoy water horizon. The water is reported to be soft, but unfortunately no analyses are available. The water is under a good head, rising 22 feet above tide. at Chaptico. This is perhaps the limit of height to which this water will rise and it should not be expected to rise quite to this height. Fifteen feet is nearer the level to which this water will ordinarily rise above tide.

St. Mary's County is thus shown to possess two valuable water levels that can be rather definitely located and correlated, both levels supplying good water and both having good heads. The Survey does not possess much information regarding the depletion of the stored water, but at several places decreases have been noted. In the Eocene wells around Oakley, Palmers, Compton, and Blakistone Island there has been a steady although slight decrease in flow, and around Piney Point, St. George Island, and St. Inigoes the flow of Calvert water has also diminished, in fact the well at St. Inigoes Manor has entirely ceased to overflow. These instances merely make more evident the insistent need for some regulation of the use of underground waters. When one considers the slow rate at which the underground water moves, probably less than 2 feet an hour, and that one well flowing only 3 gallons a minute will exhaust over

4000 gallons in a day, it will at once be seen that unless measures are taken to check the present great and widespread waste of these waters the supply must soon show disturbing diminution and eventually actual exhaustion of many wells.

Non-Artesian Waters

The majority of the inhabitants of the county depend upon springs and shallow wells for water for domestic purposes.

SPRINGS. The nature of the topography of the region with many stream valleys cut almost to sea level combined with the gentle dip of the different beds of varying permeability afford excellent conditions for the development of springs. The ground water sinking through the porous Pleistocene deposits until the less porous beds of the Miocene are encountered, flows along the contact until it is tapped by some valley slope where it issues as a line of seepage or as a spring. A large percentage of the ground water is not checked at the contact of the Pleistocene and Miocene but passes downward through the sandy layers of the latter formation until its farther progress is checked by more argillaceous beds along which it flows until the layer outcrops at the surface. The more deep-seated springs of the latter sort which penetrate Miocene beds are apt to be purer than the shallow springs and furnish an unfailing supply of excellent water. In addition to the increased danger of contamination in the shallower springs, they are very apt to fail in dry weather.

Some of the springs are remarkable because of the large quantity of exceptionally pure water which issues from them, and also because of their continuous flow since the earliest settlement of the state with probably undiminished volume. The most famous one is Governor's Spring, a short distance east of St. Mary's City, which was the first permanent settlement in Maryland and for a long time its capital. Another spring, equally well known, is the excellent spring at Charlotte Hall which has long furnished the supply of water for the boy's school at that place.

SHALLOW WELLS.-Shallow wells are the common source of water for the agricultural population, and these usually supply a good water in sufficient quantities for domestic use. Except on the top of narrow divides between deep valleys, the ground-water level lies near the surface

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and an abundance of water can be obtained from dug wells of shallow depth. On the narrow divides, however, the water table during dry seasons sinks almost to sea level and thus necessitates wells of considerable depth. On the other hand, on the broad, low-lying flats bordering the Potomac dug wells rarely need to be over 20 feet in depth and sometimes the water in them rises nearly to the surface. The water in these shallow wells is very apt to contain impurities, usually of organic origin, although iron salts are also liable to be present in greater or less amounts. Some of the wells on St. George Island are only 12 feet deep and the water in these is more or less brackish because of seepage from the river. The location of shallow wells in or near settlements should be given very careful consideration, since most of the villages are on hills and household drainage is especially liable to contaminate the wells.

COUNTIES OF CENTRAL MARYLAND
HARFORD COUNTY

Harford County lies to the west of the headwaters of Chesapeake Bay and extends to the Pennsylvania line. Over three-quarters of its area is in the Piedmont Plateau district and is a gently rolling upland, while the southeastern quarter is in the Coastal Plain district and is low and flat.

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The Piedmont portion of the county is formed by the very ancient crystalline and sedimentary rocks of igneous and metamorphic origin which are much folded and faulted. These comprise quartzite, slates,

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