There is a huge belt of red land, known as "the red sandstone formation," extending from the Potomac through a part of each of the counties of _Loudoun_, Fairfax, Prince William, Fauquier, Culpeper, and Orange, which, with judicious cultivation, might be rendered liberally productive. Professor W. B. Rogers, in his report to the legislature of Virginia, in 1840, described it under the head of the "secondary formation in the northern district." "The general form of this area," he wrote, "is that of a prolonged triangle, extending in a direction from SSW. to NNE., having its apex at the southern extremity, and gradually expanding until it reaches the Potomac. Measured at a point on the Potomac between the mouths of Goose Creek and Broad Run, its length is about 80 miles. Its greatest breadth, as measured near the Potomac, and parallel to the road leading from Leesburg to Dranesville, is about 15 miles. This, in round numbers, gives 600 square miles for the area of this region."
Bottom lands of inexhaustible fertility and rich upland loams are commonly met with north and south of Leesburg for a considerable distance on either side of the turnpike leading from Point of Rocks, Md., at one extremity of the County to Middleburg at the other.
Limestone occurs in vast quantities throughout this zone, and there are present all the propitious elements that will be enumerated in the treatment of the soils of other areas.
The land here is in a high state of cultivation and, according to its peculiarly varying and unalterable adaptability, produces enormous crops of all the staple grains of the County.
The soil in the vicinity of Oatlands, included in this zone, is stiff and stony, except such as is adjacent to water courses, or the base of hills, where it is enriched by liberal supplies of decayed matter, which render it loamy and inexhaustible. In the main, it is of a generous quality, so pertinaciously retaining fertilizers as to withstand the washing of the heaviest rains. Still it is an anomaly that some of the richest areas in this region will not produce wheat; while, in the cultivation of rye, oats, and corn, satisfactory results are almost invariably obtained. Likewise there are but a few parcels whereon white clover does not grow spontaneously and in the greatest abundance. Than these, better pasture lands are found nowhere east of the Blue Ridge. Limestone occurs here in vast quantities.