10 
THE CABINET OF NATURAL HISTORY, 
round the half of a circle, it is precipitated from the point 
in a current diagonally across its own channel, to another 
curve of the same uniformity upon the opposite shore. 
These curves are so regular, that the boatmen and Indians 
calculate distances by them. Opposite to each of them, 
there is always a sand-bar, answering, in the convexity of 
its form, to the concavity of “the bend,” as it is called. 
The river, by continually wearing these curves deeper, 
returns, like many other streams before described, on its 
own tract, so that a vessel in some places, after sailing for 
twenty-five or thirty miles, is brought round again to 
within a mile of the place whence it started. When the 
waters approach so near to each other, it often happens at 
high floods that they burst through the small tongue of 
land; and, having insulated a portion, rush through what is 
called the “ cut off” with great velocity. At one spot 
called the “ grand cut off,” vessels now pass from one 
point to another in half a mile, to a distance which it for- 
merly required twenty miles to reach. After the flood 
season, when the river subsides within its channel, it acts 
with destructive force upon the alluvial banks, softened 
and diluted by the recent overflow. Several acres at a 
time, thickly covered with wood, are precipitated into the 
stream; and the islands formed by the process before 
described, lose large portions of their outer circumfer- 
ence. 
Some years ago, when the Mississippi was regularly 
surveyed, all its islands were numbered, from the conflu- 
ence of the Missouri to the sea; but every season makes 
such revolutions, not only in the number but in the magni- 
tude and situation of these islands, that this enumeration is 
now almost obsolete. Sometimes large islands are entirely 
melted away — at other places they have attached them- 
selves to the main shore, or, which is the more correct 
statement, the interval has been filled up by myriads of 
logs cemented together by mud and rubbish. When the 
Mississippi and many of its great tributaries overflow their 
banks, the waters, being no longer borne down by the 
main current, and becoming impeded amongst the trees 
and bushes, deposit the sediment of mud and sand with 
which they are abundantly charged. Islands arrest the 
progress of floating trees, and they become in this manner 
reunited to the land; the rafts of trees, together with mud, 
constituting at length a solid mass. The coarser portion 
subsides first, and the most copious deposition is found 
near the banks where the soil is most sandy. Finer par- 
ticles are found at the farthest distances from the river, 
where an impalpable mixture is deposited, forming a stiff 
unctuous black soil. Hence the alluvions of these rivers 
are highest directly on the banks, and slope back like a 
natural “glacis” towards the rocky cliffs bounding the 
great valley. The Mississippi, therefore, by the continual 
shifting of its course, sweeps away, during a great portion 
of the year, considerable tracts of alluvium which were 
gradually accumulated by the overflow of former years, 
and the matter now left during the spring-floods will be at 
some future time removed. 
One of the most interesting features in this basin is “ the 
raft. ” The dimensions of this mass of timber were given 
by Darby, in 1816, as ten miles in length, about two 
hundred and twenty yards wide, and eight feet deep, the 
whole of which had accumulated, in consequence of some 
obstruction, during about thirty-eight years, in an arm of 
the Mississippi called the Atchafalaya, which is supposed 
to have been at some past time a channel of the Red River, 
before it intermingled its waters with the main stream. 
This arm is in a direct line with the direction of the 
Mississippi, and it catches a large portion of the drift wood 
annually brought down. The mass of timber in the raft is 
continually increasing, and the whole rises and falls with 
the water. Although floating, it is covered with green 
bushes, like a tract of solid land, and its surface is enli- 
vened in the autumn by a variety of beautiful flowers. 
Notwithstanding the astonishing number of cubic feet of 
timber collected here in so short a time, greater deposits 
have been in progress at the extremity of the delta in the 
Bay of Mexico. Unfortunately for the navigation of the 
Mississippi, some of the largest trunks, after being cast 
down from the position on which they grew, get their roots 
entangled with the bottom of the river, where they remain 
anchored, as it were, in the mud. The force of the current 
naturally gives their tops a tendency downwards, and by 
its flowing past, soon strips them of their leaves and 
branches. These fixtures, called snags or planters, are 
extremely dangerous to the steam-vessels proceeding up 
the stream, in which they lie like a lance in rest, con- 
cealed beneath the water, with their sharp ends pointed 
directly against the bow of vessels coming up. For the 
most part these formidable snags remain so still, that they 
can be detected only by a slight ripple above them, not 
perceptible to inexperienced eyes. Sometimes, however, 
they vibrate up and down, alternately showing their heads 
above the surface and bathing them beneath it. So im- 
minent is the danger caused by these obstructions, that 
almost all the boats on the Mississippi are constructed on 
a particular plan, to guard against fatal accidents. They 
have at their bows, a place called a snag-chamber, and 
confined only to boats calculated for the navigation of this 
river; the chamber is partitioned off, about fifteen feet 
from the stem, with very stout planks, well caulked, so 
that the remainder of the vessel is completely cut off from 
this room; and consequently, should a snag strike the 
