[Footnote 3:  “What is called Lowe’s Island, at the mouth of Sugarland Run, was formerly an island, and made so by that run separating and part of it passing into the river by the present channel, while a part of it entered the river by what is now called the old channel.  This old channel is now partially filled up, and only receives the waters of Sugarland Run in times of freshets.  Occasionally when there is high water in the river the waters pass up the present channel of the run to the old channel, and then follow that to the river again.  This old channel enters the river immediately west of the primordial range of rocks, that impinge so closely upon the river from here to Georgetown, forming as they do that series of falls known as Seneca Falls, the Great, and the Little Falls, making altogether a fall of 188 feet in less than 20 miles.”—­Memoir of Loudoun.]

[Footnote 4:  Designated in an old record as a “double-bodied poplar tree standing in or near the middle of the thoroughfare of Ashby’s Gap on the top of the Blue Ridge.”  It succumbed to the ravages of time and fire while this work was in course of preparation.]

This completes an outline of 109 miles, viz:  19 miles in company with Fairfax, 10 with Prince William, 17 with Fauquier, 26 with Clarke and Jefferson, and 37 miles along the Potomac.

TOPOGRAPHY.

Loudoun County is preeminently a diversified region; its surface bearing many marked peculiarities, many grand distinctive features.  The broken ranges of hills and mountains, abounding in Piedmont Virginia, here present themselves in softly rounded outline, gradually sinking down into the plains, giving great diversity and picturesqueness to the landscape.  They are remarkable for their parallelism, regularity, rectilineal direction and evenness of outline, and constitute what is by far the most conspicuous feature in the topography of Loudoun.  Neither snow-capped nor barren, they are clothed with vegetation from base to summit and afford fine range and pasturage for sheep and cattle.

The main valleys are longitudinal and those running transversely few and comparatively unimportant.

The far-famed Loudoun valley, reposing peacefully between the Blue Ridge and Catoctin mountains, presents all the many varied topographic aspects peculiar to a territory abounding in foothills.

The Blue Ridge, the southeasternmost range of the Alleghanies or Appalachian System presents here that uniformity and general appearance which characterizes it throughout the State, having gaps or depressions every eight or ten miles, through which the public roads pass.  The most important of these are the Potomac Gap at 500 feet and Snickers and Ashby’s Gap, both at 1,100 feet.  The altitude of this range in Loudoun varies from 1,000 to 1,600 feet above tide-water, and from 300 to 900 feet above the adjacent country.  It falls from 1,100 to 1,000 feet in 4 miles south of the river, and then, rising sharply to 1,600 feet, continues at the higher series of elevations.  The Blue Ridge borders the county on the west, its course being about south southwest, or nearly parallel with the Atlantic Coast-line, and divides Loudoun from Clarke County, Virginia, and Jefferson County, West Virginia, the line running along the summit.