150 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES

plished by the Monocacy river and its numerous tributaries, the latter
flowing in nearly parallel west and east courses from Parr's Ridge and
the Catoctin Mountain. The deeper portions of the valley are con-
siderably to the west of the centre of the district, and as a result the
streams upon the east are longer and of greater volume than those
upon the west. The water-ways at a distance from the main valley
flow in marked channels, which are frequently deeply cut in the land.

THE APPALACHIAN REGION.

The Appalachian Region borders the Piedmont Plateau upon the
west and extends to the western limits of the state. It comprises
about 2000 square miles, or somewhat less than one-fourth of the area
of the state and has a width of about 115 miles from east to west.
It includes the western portion of Frederick and all of Washington,
Allegany and Garrett counties. This region consists of a series of
parallel mountain ranges with deep valleys which are cut, nearly at
right angles, throughout much of the distance, by the Potomac river.
Many of the ranges exceed 2000 feet, while some reach 3000 feet
and more in the western portion of the mountainous area. The
country illustrates in an exceptional manner the type of adjusted
drainage. The Appalachian Region is divided into three distinct
physiographic districts, based upon clearly defined geological differ-
ences, viz., an eastern (Blue Ridge and Great Valley), a central (Appa-
lachian Mountains proper), and a western (Alleghany Mountains)
division.

The eastern division comprises the area between the Catoctin and

North Mountains and has a width of about 25 miles from east to west.
Along the eastern border of this region the Catoctin Mountain ex-
tends from north to south, beginning in the highlands of Pennsylvania
and reaching to the Potomac river at Point of Rocks. This range
reaches an altitude of 1800 feet in Maryland. Succeeding the Catoc-
tin Mountain upon the west is the Middletown Valley, with an ele-
vation of 500 feet at Middletown. The valley drains southward
into the Potomac river through the Catoctin creek and its tributaries,
which receive their waters from the western flank of the Catoctin