western border. The Potomac then becomes the dividing line between
Loudoun County, and Frederick and Montgomery counties, Maryland; "and
that State, claiming the whole of the river, exercises jurisdiction
over the islands as well as the river."

[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.