wn by the Mississippi
and its tributaries, is a subject of geological interest, not merely as
illustrating the manner in which abundance of vegetable matter becomes,
in the ordinary course of nature, imbedded in submarine and estuary
deposits, but as attesting the constant destruction of soil and
transportation of matter to lower levels by the tendency of rivers to
shift their courses. Each of these trees must have required many years,
some of them centuries, to attain their full size; the soil, therefore,
whereon they grew, after remaining undisturbed for long periods, is
ultimately torn up and swept away.

It is also found in excavating at New Orleans, even at the depth of
several yards below the level of the sea, that the soil of the delta
contains innumerable trunks of trees, layer above layer, some prostrate,
as if drifted, others broken off near the bottom, but remaining still
erect, and with their roots spreading on all sides, as if in their
natural position. In such situations they appeared to me to indicate a
sinking of the ground, as the trees must formerly have grown in marshes
above the sea-level. In the higher parts of the alluvial plain, for many
hundred miles above the head of the delta, similar stools and roots of
trees are also seen buried in stiff clay at different levels, one above
the other, and exposed to view in the banks at low water. They point
clearly to the successive growth of forests in the extensive swamps of
the plain, where the ground was slowly raised, year after year, by the
mud thrown down during inundations. These roots and stools belong
chiefly to the deciduous cypress (_Taxodium distichum_), and other
swamp-trees, and they bear testimony to the constant shifting of the
course of the great river, which is always excavating land originally
formed at some distance from its banks.

_Formation of lakes in Louisiana._.--Another striking feature in the
basin of the Mississippi, illustrative of the changes now in progress,
is the formation by natural causes of great lakes, and the drainage of
others. These are especially frequent in the basin of the Red River in
Louisiana, where the largest of them, called Bistineau, is more than
_thirty miles_ long, and has a medium depth of from _fifteen_ to
_twenty_ feet. In the deepest parts are seen numerous cypress-trees, of
all sizes, now dead, and most of them with their tops broken by the
wind, yet standing erect under water. This tree resists the