progressively deeper, though there are local exceptions to this general rule where water-bearing sands lie near the surface. This condition is most commonly found on the broad areas of nearly flat terraces, though it is sometimes found on the slopes. The deepest wells are located on high hills where permanent supplies can only be obtained by sinking the wells to sands or gravels overlain by heavy beds of clay and marl.

Many of the shallow wells obtain water from some of the formations of Pleistocene age that form the terraces. On the lower terraces the shallow wells usually obtain their supplies within the Talbot formation, but on the higher terraces the deeper wells often penetrate to the older geological formations, although the Brandywine, through its wide extent, will furnish water from its base.

The quantity of water in the shallow wells is seldom large, amounting in most wells to less than 10 feet and in many to only 3 or 4 feet. Some of the wells that obtain water from the surficial sands are affected by the amount of rainfall, and the quantity of water varies from several feet during rainy seasons to little or none during droughts. In the deeper wells there is less variation in quantity of water, the level remaining relatively constant despite the change in amount of rainfall. Even after making allowance for variations it is usually possible to obtain large enough supplies from shallow wells to meet all the demands of the rural population.

The quality of the water from shallow wells varies with the depth and location of the well, and there are local differences which appear to be independent of depth and location. The quantity of organic matter is controlled by local conditions. In some places the water-bearing beds contain decaying vegetation which gives the water a disagreeable odor and may also affect the taste. This condition is most common in the Talbot formation, but it has also been noted in some of the other horizons. Very shallow wells or those improperly cased may receive organic matter by the entrance of contaminated surface water, but fortunately this condition may be remedied by properly and tightly casing the well or by sinking the well to water-bearing sands or gravels covered by impervious clays or marls, and then inserting water-tight casings. The amount and

character of the inorganic matter in water from shallow wells is controlled by the nature of the soluble materials in the water-bearing beds and the opportunities for solution. The most common substances are those present in nearly all ground water, such as lime, magnesia, iron, etc. These substances make the water hard and the iron is especially annoying because it forms a red or yellow deposit when the water is exposed to the air or boiled. Iron is found in much of the shallow well water, especially since there are nodules or boulders of the ore abundantly scattered through the Pleistocene sands and gravels.

CHARLES COUNTY

Charles County lies wholly within the Coastal Plain of Southern Maryland. Much of the country lies at a considerable elevation above tide for a Southern Maryland county, and the surface, originally flat terrace plains, is now much dissected by the network of minor streams, only the flat-topped divides preserving the original level surface.

The major elevations of these divides gradually increase toward the north and northwest from 100 feet on Cobbs Neck in the southern part of the county to 180 to 220 feet near the Prince George's County boundary.

The geological formations exposed in the county range in age from the Lower Cretaceous to the Pleistocene. The former are exposed in a narrow belt along the Potomac in the northwestern part of the county,

extending from Marshall Hall to Stump Neck. The materials are sands and clays of limited outcrop. The Eocene greensands, sands, and clays are exposed along the Potomac from Mattawoman Creek southward and in most of the stream valleys throughout the county, giving rise to light yellow loams, excellent for truck and canning crops. These formations underlie all of the county to the southeast of the Cretaceous belt. The Calvert formation of the Miocene, which overlies the Eocene, forms a widespread mantle of sandy clays throughout the county except where it is hidden from view by the surficial terrace deposits of the Brandywine, Sunderland, Wicomico, and Talbot formations. The Brandywine forms the surface of the flat-topped divide forming the axis of the peninsula of Southern Maryland and extends southward into the northeastern part of the county from Prince George's County as far as La Plata and Hughesville. Its materials are sands and gravels, and these give rise to the poorest farming lands in the county. Bordering the Brandywine terrace at a lower level and separated from it by a more or less well-marked escarpment or steep slope are found the sandy loams of the Sunderland. formation, which give rise to excellent tobacco and trucking soils. These form the surface over wide areas in the Cross Roads, Hilltop, La Plata, and Allens Fresh Election Districts. Lying at a still lower level and not especially well developed, except in the southern half of the Cross Roads Election District, are found the sands and gravelly loams of the Wicomico formation. The lowest-lying terrace of sand, clay, and gravel known as the Talbot formation forms a narrow border to the next highest or Wicomico terrace and is not extensively developed in Charles County except on Tayloe, Cedar Point, and Cobbs Neck.

SURFACE WATERS

More than half the county boundary is formed by the waters of the Potomac, from which the three large tidal estuaries of the Nanjemoy, Port Tobacco, and Wicomico, extend northward into the county. These are all tidal and therefore not potable. The smaller streams are numerous and generally distributed, but the flow is limited and all are liable to pollution. Since the industries of the region are practically restricted to agriculture and fishing, there is not likely to be any local congestion of population which will require the use of surface waters.

UNDERGROUND WATERS

Artesian Waters

With the exception of the wells at Indian Head and one at Allens Fresh, all of the artesian water in use in Charles County comes from beds of Eocene age. In this account of the artesian waters the shallow wells which draw from the Calvert or basal Chesapeake water level are disregarded since the head is very small and data regarding this class of wells are very meager.

The wells drawing from the Eocene water level form the majority of the deep wells in the county. The water seems to be confined to one level, probably at the base of the Aquia. The water is reported soft, a feature not common to the Aquia water on the Eastern Shore but perhaps due here to the nearness of outcrops. This horizon is tapped at Port Tobacco at 160 feet, at Nanjemoy at 175 feet, at Chapel Point at 236 feet, where the well does not flow due to the elevation; at Popes Creek at 202 feet, at Newport at 248 feet, at Wayside and Tompkinsville at 267 and 265 feet. These wells except the one at Chapel Point all flow and all of them yield a good water. This bed probably underlies all of the county southeast of a line drawn a few miles back of the northwestern shore along the Potomac, becoming increasingly important southeastward.

A well at Benedict is 346 feet deep and has a small flow of hard water. This well also draws from the Aquia; the slightly greater depth than would be expected is probably the result of a slight thickening of the deposits. A well near Allens Fresh is 412 feet deep and has a flow of about 13 gallons a minute of soft water. This well has encountered the stream in the Magothy which has been mapped by Darton, Shattuck, and Miller as the main stream of the Upper Cretaceous. This level was also tapped by the town well at La Plata, which was sunk to a depth of 560 feet with the mouth of the well at an elevation of 190 feet. The water in this well stood 125 feet below the surface, an impossible depth to work a suction pump, but not too deep for an air cylinder. The wells at the Naval Proving Ground, Indian Head, are drawing from a sand in the Patuxent formation. The log of the first of these wells, taken from Darton,' is given below.

1 Darton, N. H. Artesian Well Prospects in Atlantic Coastal Plain, Bull. U. S. Geological Survey No. 138, 1896, pp. 134, 135.

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