le than lower down. The gravity of
particles, therefore, worn from the bed and sides of the channel above,
unless the current be exceedingly strong, is greater than the buoyant
capacity of the water, and falls to the bottom, along which, sometimes,
it is forced by the abrasion of the water, until it meets some
obstruction, which gathers the particles into shoal formations. This
fact causes much inconvenience in the navigation of the upper rivers.

It is not until we reach the confluence of the streams of Southern
Illinois and Missouri, that the sediment of the river becomes striking.
Those streams, freighted with the rich loam and vegetable matter of the
prairies of the east and west, soon change entirely the appearance of
the Mississippi. Above the Missouri, the river is but slightly tinged;
and indeed, after that great current enters, for some distance the two
run side by side in the same channel, and yet are divided by a very
distinct line of demarcation. It is only after the frequent sinuosities
of the channel, that the two waters are thrown into each other and
fairly blend. The sedimentary condition of the Missouri is so great that
drift floating upon its muddy surface, by accretion becomes so heavily
laden with earthy matter that it sinks to the bottom. This precipitation
of drift has taken place to such an extent, that the bed of the Missouri
is in many places completely covered to a great depth by immense fields
of logs. Of all the silt thrown into the Mississippi, the Missouri
furnishes about one third.

After receiving the Missouri, next enters the Ohio. The water of this
river is less impregnated than the Missouri, though not by any means
free from silt. The country through which it flows is mountainous, and
the soil hard, and does not afford the same facility of abrasive action
as that of the other rivers.

From the mouth of the Ohio, the Mississippi pursues a course of nearly
four hundred miles, when it receives the turbid waters of the White and
Arkansas Rivers. In the intervening distance a large number of small
currents, more or less largely sedimentary, according to the character
of the country through which they run, enter the Mississippi, in the
aggregate adding materially to the sediment of the receiving stream. The
White and Arkansas carry in their waters a large amount of
unprecipitated matter. In this vicinity, too, sets in that singular
system of natural safeguards of the surrounding country, t