THE southerly branch of the Ohio River, and one of its chief
affluents, is made by the union of the West Fork and Tygart Valley
rivers, in the county of Marion, state of Virginia, the united waters
of which flow north into Pennsylvania as the Monongahela River, and is
there joined by the Cheat River, its principal tributary. The
Monongahela unites with the Alleghany to form the Ohio, at Pittsburgh,
Pennsylvania. The length of the Monongahela, without computing that of
its tributaries, is about one hundred and fifty miles; but if we
include its eastern fork, the Tygart Valley River, which flows from
Randolph County, Virginia, the whole length of this tributary of the
Ohio may exceed three hundred miles. It has a width at its union with
the Alleghany of nearly one-fourth of a mile, and a depth of water
sufficient for large steamboats to ascend sixty miles, to Brownsville,
Pennsylvania, while light-draught vessels can reach its head, at
Fairmont, Virginia.

The northern branch of the Ohio, known as the Alleghany River, has a
length of four hundred miles, and its source is in the county of
Potter, in northern Pennsylvania. It takes a very circuitous course
through a portion of New York state, and re-enters Pennsylvania
flowing through a hilly region, and at the flourishing city of
Pittsburgh mingles its waters with its southern sister, the
Monongahela.

The region traversed by the Alleghany is wild and mountainous, rich in
pine forests, coal, and petroleum oil; and the extraction from its
rocky beds of the last-named article is so enormous in quantity, that
at the present time more than four million barrels of oil are awaiting
shipment in the oil districts of Pennsylvania. The smaller steamboats
can ascend the river to Olean, about two hundred and fifty miles above