Loudoun Sandy Loam.

The Loudoun sandy loam consists of from 8 to 12 inches of a heavy brown or gray sandy loam, underlain by a heavy yellow or red loam or clay loam.  Often the subsoil contains a considerable quantity of coarse sand, making the texture much the same as that of the soil.  The sand of the soil and subsoil is composed of very coarse rounded and subangular quartz particles.  The surface material is not a light sandy loam, but is more like a loam containing considerable quantities of very coarse quartz fragments.  It is generally quite free from stones, but small areas are occasionally covered with from 5 to 20 per cent of angular quartz fragments several inches in diameter.

The Loudoun sandy loam occurs in irregular areas of considerable size in the intermediate valley between the Blue Ridge, Short Hill, and Catoctin mountains.  The largest area of the type is found in the vicinity of Round Hill.

The topography of this soil in the valley varies from gently rolling to hilly, the slopes being long and gently undulating, while along the valley walls and in the uplands it is ridgy.  Owing to the position which this type occupies, surface drainage is good.  The light texture of the soil admits of the easy percolation of water through it, and, except where the subsoil contains considerable sand, the soil moisture is well retained.  In dry weather, if the ground is cultivated, a mulch is formed, which prevents the evaporation of the soil moisture and greatly assists the crops to withstand drought.

Nearly the whole of this type is in cultivation.  Where the forest still stands the growth consists chiefly of oak.  The soil is easy to handle, and can be worked without regard to moisture content.  It is considered a good corn land, but is too light-textured for wheat, although a considerable acreage is devoted to this crop.  Corn yields at the rate of 40 or 50 bushels per acre, wheat from 12 to 15 bushels and occasionally more, and grass and clover at the rate of 1 or 2 tons per acre.  The productiveness of the soil depends greatly on the sand content of the subsoil.  If the quantity be large, the soil is porous and requires considerable rain to produce good yields.  If the clay content predominates, a moderate amount of rain suffices and good yields are obtained.  Apples, pears, and small fruits do well on this soil.

Penn Clay.

The Penn clay consists of from 6 to 12 inches of a red or reddish-brown loam, resting upon a subsoil of heavy red clay.  The soil and subsoil generally have the Indian-red color characteristic of the Triassic red sandstone from which the soil is in part derived.  From 1 to 10 per cent of the soil mass is usually made up of small sandstone fragments, while throughout the greater part of the type numerous limestone conglomerate ledges, interbedded with Triassic red sandstone, come to the surface.  In other areas of the type numerous limestone conglomerate bowlders, often of great size, cover from 10 to 25 per cent of the surface.