Part 14

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"Immediately at the western base of the Catoctin Mountain, a range of magnesian or talcose slates occur traversing its whole length.... In this range a vein of magnesian limestone is met with, and is exposed in several places. It however is narrow, in some places only a few feet in thickness, and being difficult to obtain is not much sought after for burning."

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"Along the eastern side of the valley (Loudoun) gneiss is frequently met with on the surface, and where the larger streams have worn deep valleys, it is sometimes exposed in high and precipitous cliffs. This is more particularly the case along Goose Creek and Beaver Dam. Associated with it, however, is clay slate, not so much in rock as in soil, for it being more readily decomposed is seldom found on the surface, except as soil. These two varieties are often met with side by side in thin layers, and their combination at the surface forms a peculiarly favorable soil for agricultural purposes. The gneiss from the quartz it contains makes a sandy soil, while the clay slate gives it tenacity. This happy combination is a prevailing feature of this entire valley, and renders it one of the best farming sections in Virginia.

"Another rock that is a valuable acquisition is hornblende. This kind when first taken from the ground, is always covered as with a coat of rust. This is doubtless the fact, for the oxydasion of the iron it contains gives it that appearance, and colors the soil a reddish hue in its immediate vicinity. Wherever this rock abounds, the soil is durable and the crops are usually heavy. It is sometimes met with having a fine grain, and so very hard as to be almost brittle, though generally very difficult to break, and when broken strongly resembling cast-iron, and will sometimes ring, on being struck, almost as clearly. It was used very much formerly for making journals to run mill-gudgeons upon. When found on the surface, it is usually of a rounded form...."

However, much of the rock of the valley partakes of the nature of both hornblend and gneiss, and has been aptly termed a "hornblend gneiss rock."

Beds of magnesian or talcose slate, sometimes containing crystals of sulphuret of iron, are frequently met with in this section, and at the base of Black Oak Ridge, which is composed chiefly of chlorite slate and epidote, another bed of magnesian limestone is found. Containing about 40 per cent of magnesia, it makes an excellent cement for walls, but is of little or no value as a fertilizer.

SOILS.

The soils of Loudoun vary greatly in both geological character and productiveness, every variety from a rich alluvial to an unproductive clay occurring within her boundaries. In general the soils are deep and rich and profitably cultivated.

The heavy clay soils of Loudoun are recognized as being the strongest wheat and grass soils. The more loamy soils are better for corn on account of the possibility of more thorough cultivation. However, the lands all have to be fertilized or limed to obtain the best results, and with this added expense the profit in wheat growing is extremely uncertain on any but the clay soils. The loamy soils are especially adapted to corn, stock raising, and dairying, and they are largely used for these purposes. The mountain sandstone soils, which are rough and stony, are not adapted to any form of agriculture; but for some lines of horticulture--as, for instance, the production of grapes, peaches, apples and chestnuts--or forestry they seem to offer excellent opportunities. The schist soil of the mountains, although rough and stony, is productive, easily worked, and especially adapted to apples, peaches, and potatoes. The shale and mica soils, although thin and leachy, are especially adapted to grapes, vegetables, and berries, and other small fruits. These soils should be managed very carefully to obtain the best results. They are easily worked and very quickly respond to fertilization and thorough cultivation. It is very probable that market gardening and fruit raising on these types would prove profitable. It seems, however, that peach trees are short lived on these soils. The meadow lands are low and subject to overflow, although otherwise well drained. They are best adapted to the production of corn, grass, and vegetables.

That part of the County lying east of a line drawn from the Potomac River near Leesburg, by Aldie to the Fauquier line, is much more unproductive than the western portion, partly on account of an inferior soil, and partly in consequence of an exhausting system of cultivation, once so common in eastern Virginia, i. e., cropping with corn and tobacco without attempting to improve the quality of the soil. When impoverished, the lands were thrown out to the commons.

Large tracts that formerly produced from thirty to forty bushels of corn to the acre, still remain out of cultivation, though many of the present proprietors are turning their attention to the improvement of these soils and are being richly rewarded.

In this section, particularly along Goose Creek, trap-rock occurs, sometimes covering large surfaces, at other times partially covered with indurated shale, formed from the red shale of this region which has become hardened by the heat of the intruding trap. Where this rock occurs covering large surfaces, nearly level, "the soil is a dark brown colored clay, very retentive of moisture and better adapted to grass than grain.... A deficiency of lime probably occurs here, and there may be some obnoxious ingredient present. Minute grains of iron sand are generally interspersed through this rock, and as it is not acted upon by atmospheric influences, its combination may contain some acid prejudicial to vegetation. Where this rock is thrown into more irregular elevations, and is apparently more broken up, the soil is better."

Near the Broad Run Bridge the soil is deplorably sterile. "In many places it is but a few inches in thickness, and the rock below, being compact, prevents the water from penetrating much below the surface, thus causing an excess of water in rainy weather, and a scarcity of it in fair weather. The red shale does not appear to decompose readily, as it is found a short distance beneath the surface, and the strata dipping at a low angle, prevents the water from freely descending into this kind of soil."

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.

In the Valley of Loudoun, between the Catoctin and Blue Ridge mountains, the soil is formed from gneiss, clay-slate, hornblend, greenstone, and quartz. The happy combination of these materials produces a most excellent and durable soil, containing, in fair proportions, alumina, silex, potash, lime, and other fertilizing minerals. Certain fertilizers have been successfully employed in improving its natural fertility, and when it is partially exhausted by excessive tillage, rest alone will restore it.

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.

This latter phase occurs in the vicinity of the Potomac River near Point of Rocks, Md., and near the Potomac, 3 miles north of Leesburg, and in these places the heavier phase of the type occurs, the clay often being very near the surface. In other parts of the County, where the limestone conglomerate is not so preponderant, or where it lies deeper and is mostly unexposed, the surface soil is deeper, often consisting of 18 inches of loam. The land is locally termed "limestone land." Near Catoctin Mountain the rocks seem to have weathered to considerable depth, there being no exposures or outcrops. Here the soil has been washed away from some of the more elevated small areas, and the heavy red clay subsoil is exposed.