History and Comprehensive Description of Loudoun County, Virginia | Page 6

physiography of this valley--so called only by reason of its relation to the mountains on either side--has been made elsewhere in this department.
Immediately south of Aldie, on Little River, near the point of interruption of Catoctin Mountain, another range commences and extends into Fauquier County. It is known as "Bull Run Mountain," but might rightly be considered an indirect continuation of the elevation of the Catoctin, its course and some of its features corresponding very nearly with that mountain save only that it is higher than any of the ranges of the latter, excepting the western.
East of the Catoctin the tumultuous continuity of mountains subsides into gentle undulations, an almost unbroken succession of sloping elevations and depressions presenting an as yet unimpaired variety and charm of landscape. However, on the extreme eastern edge of this section, level stretches of considerable extent are a conspicuous feature of the topography.
Three or four detached hills, rising to an elevation of 150 or 200 feet above the adjacent country, are the only ones of consequence met with in this section.
COMPARATIVE ALTITUDES.
The hilly character of Loudoun is clearly shown by the following exhibit of the elevation of points and places above tide-water. The variations of altitude noted in this schedule are based upon conflicting estimates and distinct measurements made at two or more points within a given circumference and slightly removed one from the other.
Feet. Sterling 415 Ashburn 320 Leesburg 321 to 337 Clarke's Gap 578 to 634 Hamilton 454 to 521 Purcellville 546 to 553 Round Hill 558 Bluemont 680 to 730 Snicker's Gap 1,085 Neersville 626 Hillsborough 550 Waterford 360 Mount Gilead 600 Oatlands 270 Little River, near Aldie 299 Middleburg 480 Potomac River, near Seneca Dam 188 Potomac River, at Point of Rocks 200 Potomac River, at Harper's Ferry 246
The whole of the county east of the Catoctin Mountain varies from 200 to 350 feet. The eastern base of the Blue Ridge has an elevation of about 730 feet, and the highest peak of that range in Loudoun rises 1,600 feet above tide-water.
The Short Hills have an approximate altitude of 1,000 feet, while that of the Catoctin Mountain varies from 300 to 700 feet. The valley between the Blue Ridge and Catoctin Mountains varies from 350 to 730 feet in elevation.
From many vantage points along the Blue Ridge may be obtained magnificent views of both the Loudoun and Shenandoah valleys. The eye travels entirely across the fertile expanse of the latter to where, in the far distance, the Alleghany and North Mountains rear their wooded crests. A few of the summits offer even more extensive prospects. From some nearly all of Loudoun, with a considerable area of Fairfax and Fauquier, is in full view. Other more distant areas within visionary range are portions of Prince William, Rappahannock, and Culpeper counties, in Virginia, Frederick and Montgomery counties, in Maryland, and even some of Prince George County, east of Washington City. Westward, the view embraces Shenandoah, Frederick, Clarke and Warren counties, in Virginia, Berkeley and Jefferson counties, in West Virginia, Washington County, in Maryland, and some of the mountain summits of Pennsylvania.
DRAINAGE.
The drainage of Loudoun can be divided into two provinces. One is the Potomac province, which is drained by a system of small tributaries of that stream. Its elevations are quite uniform and are referable to that master stream, whose grade is largely determined by its great basin beyond the "Catoctin belt." The second province is the region drained by smaller streams, chief of which is Goose Creek. In this province the drainage lines head entirely within the "Catoctin belt," and the elevations are variable according to the constitution of the rocks in the belt itself.
The tributaries by which the drainage of the two provinces is effected are Catoctin Creek, North Fork Catoctin Creek, South Fork Catoctin Creek, Little River, North Fork Goose Creek, Beaver-dam Creek, Piney Run, Jeffries Branch, Cromwells Run, Hungry Run, Bull Run, Sycoline Creek, Tuscarora Creek, Horse Pen Run, Broad Run, Sugarland Run, Elk Lick, Limestone Branch, and as many lesser streams.
The general slope of the county being to the northeast, the waters, for the most part, naturally follow the same course, as may be readily perceived by reference to maps of the section. The streams that rise in the Blue Ridge mostly flow to the eastward until they approach the Catoctin Mountain, where they are then deflected more toward either the north or south to pass that range by the Northwest Fork and Goose Creek, or by the Catoctin Creek which falls into the Potomac above Point of Rocks. East of Catoctin Mountain the streams pursue a more or less direct northern course.
Goose Creek, a right-hand branch of the Potomac River, is a considerable stream, pursuing a course of about fifty miles from its source in Fauquier County