sterly
course, to the Rocky
Mountains, thence taking a line
separating the headwaters of
the Red, Arkansas, and tributary
streams, on the east, from
the Rio Grande and tributaries
toward the south, and the Colorado _Miles._
toward the west, say, 1,300

Thence, pursuing the dividing
summit of the Rocky Mountains,
to the Marias, tributary
to the Missouri, in Dakota, say, 700

Thence, including the headwaters
of the Missouri, and taking
direction southeasterly,
dividing the tributaries of the
Red River of the North from
those of the Missouri to the
source of the Minnesota; thence
northeasterly, dividing the rivulets
of the head lakes, Itasca,
Cass, etc., from those confluent
to the Red River of the North,
separating the headwaters of
the St. Croix from currents tributary
to Lake Superior; thence
embracing the confluent streams
to the Mississippi in Wisconsin,
Northern Illinois, and Indiana,
to the Kankakee branch of the
Illinois, say, 2,000

Thence, dividing the streams of
the Lakes from those emptying
into the Ohio as far as the extreme
source of the Alleghany,
say, 400

Thence along the dividing summit
of the Atlantic slope to the
source of the Tennessee; thence
dividing the streams tending
toward the Gulf, to the mouth
of the Mississippi, and thence
to starting point, say, 1,700
______
Making an aggregate circuit of 6,100

Within this extensive limit we find, from surveys, the following
aggregate area in square miles, estimated by valleys:

_Square Miles._

The valley of the Ohio, 200,000

The valley of the Mississippi
proper, 180,000

The valley of the Missouri, 500,000

The valley of the Lower Mississippi, 330,000
_______
Total area, 1,210,000

As a natural consequence of the drainage of this immense area, the
Mississippi receives into its waters a large amount of suspended earthy
matter. This, however, does not very strikingly appear on the upper
river, its own banks and those of its tributaries being more of a
gravelly character and less friab