The topography consists of a gently rolling to nearly level plain, and there are no steep slopes or rough areas.  Drainage in this type is excellent, the easy slopes allowing a gradual flow of water from the surface without undue erosion, except with very heavy rains on the steeper slopes.  The loamy subsoil allows a ready but not too rapid percolation of surplus soil moisture, and never gets soggy or in a cold, sour condition.  Numerous small streams extend throughout the area of this type, allowing a rapid removal of all surplus water into the Potomac River, the chief drainageway of the County.  Along these streams, which in all cases have cut out beds some 10 to 30 feet below the surrounding plain, the slopes are gradual.

The original growth on the Penn loam was a forest of oak, hickory, and walnut, but at the present time nearly all of the type is cleared and farmed.  The soil is not naturally very productive, but is prized on account of its great susceptibility to improvement, its quick responsiveness to fertilization, and its easy cultivation and management.  The surface is smooth and regular, and the absence of stones, together with the loamy texture of the soil, makes it easy to maintain good tilth.  Any addition of fertilizers or lime is immediately effective, and by judicious management the type may be kept in a high state of productiveness.  Many fine farms with good buildings are to be seen on this type.  The crops grown are corn, wheat, grass, clover, apples, and small fruits.  Grazing, stock raising, and dairying are practiced to some extent.  The land yields from 40 to 60 bushels of corn, from 10 to 15 or more bushels of wheat, and from 1 to 2 tons of hay per acre.

Cecil Loam.

The soil of the Cecil loam consists of from 8 to 12 inches of a brown or yellow loam.  The subsoil consists of a heavy yellow or red loam, or occasionally clay loam.  The soil and subsoil are usually free from stones, but occasional areas have from 5 to 30 per cent of angular quartz or schist fragments on the surface.  Often a mica-schist enters into the composition of the subsoil, giving it a soft and greasy feel.

The greater part of the intermediate valley or baselevel plain of the Catoctin Belt consists of the Cecil loam, and it occurs here as one large, connected area, inside of which are small areas of Cecil clay, Loudoun sandy loam, and Iredell clay loam.  A considerable portion of the Catoctin Mountain also consists of the Cecil loam.  In extent this is the most important soil type in Loudoun, covering about 33 per cent of the total area.

The Cecil loam, owing to its rolling character, is well drained throughout.  Many small streams traverse it, affording ample outlets for surface water.  The gently rolling areas are not generally subject to excessive erosion, but the steeper slopes wash badly, deep gullies and ditches being formed on the hillsides.  Especially subject to erosion are the areas in which the subsoil contains a relatively large proportion of mica fragments.  The soil and subsoil, though quite loamy, retain enough moisture in seasons of moderate rainfall to supply all growing crops.