omewhat complicated by the wash from the mountain, which
consists principally of subangular quartz fragments, from 1 to 4
inches in diameter. This rock sometimes forms as much as 30 or 40 per
cent of the soil mass. This phase is called "gravelly land," and is
hard to cultivate on account of its heavy texture and stony condition,
although it is inherently productive.

This type occurs in one irregular-shaped area, about 15 miles long,
varying from less than 1 mile to 3 or 4 miles in width, being cut by
the Potomac River just east of Point of Rocks, Md. It thus lies in the
central part of the County, in the Piedmont Plateau, extending from
immediately north of Leesburg, and skirting the eastern foot of
Catoctin Mountain.

The general surface drainage is good, there being many small streams
flowing through the type and emptying into the Potomac River. The
stream beds are but little lower than the surface of the surrounding
land, while the slopes are long and gentle. Excessive erosion scarcely
ever occurs. The heavier phase of the type would undoubtedly be
improved by tile draining, as it is usually lower lying than the
lighter phase. The heavier phase bakes and cracks in dry weather much
the same as the heavy limestone soils of the Shenandoah Valley, but
with the lighter phases, where the soil covering is deeper, good tilth
is easily maintained throughout the growing season.

Corn, wheat, clover, and grass are the crops grown, of which the
yields are as follows: Corn, from 40 to 60 bushels per acre; wheat,
from 15 to 25 bushels per acre, and clover and grass, from 1-1/2 to
2-1/2 tons of hay per acre.

The Penn clay is the most highly prized soil of the Piedmont region of
Loudoun and brings the highest prices.

_Penn Stony Loam._

The Penn stony loam consists of from 8 to 12 inches of a red or
grayish heavy loam, somewhat silty, underlain by a heavier red loam.
From 10 to 60 per cent of gray and brown fragments of Triassic
sandstone, ranging from 1 to 6 inches in thickness, cover the surface
of the soil. The color is in general the dark Indian-red of the other
soils derived from Triassic sandstone, being particularly marked in
the subsoil.

This type occurs in the southeastern part of Loudoun, on the Piedmont
Plateau. It occupies three small areas whose total extent probably
does not exceed two and one-half square miles. It is closely
associated with the Penn loam and grades gradually into that type. The
only gr