disturbance of the natural course of that river.
The Atchafalaya, inclining to the E. of S., enters
the bay of the same name in the Gulf of Mexico.
The outlet Plaquemine leaves the Mississippi
128 miles below the outlet Atchafalaya. Thirty-
one miles below the Plaquemine, and 81 above
New Orleans, is the outlet of La Eourche, which
also communicates with the ocean. Below this
there are numerous small streams leaving the
Mississippi at ditferent points. On the E. side
the principal outlet is the Iberville, which passes
off a little below Baton Rouge, going through
Lakes Maurepas, Ponchartrain, and Borgne, into
the Gulf of Mexico. In times of flood this out-
let carries off considerable water. Between this
outlet on the E. and Atchafalaya on the W. is
included what is called the Delta of the Missis-
sippi. At the distance of 105 miles below New
Orleans, by the course of the river, and of 90
miles in a direct line, this majestic river enters
the Gulf of Mexico by its several mouths, the
principal of which is the N. E. pass, called the
Balize, 29° T 25" N. lat., and 89° 10' VV. Ion.,
and the S. W. pass, 29° 8' N. lat., and 89° 25'
W. Ion. Most of the vessels enter and leave the
river by the Balize. The depth of water on the
bar, at each of these passes, is from 12 to 17 feet,
but much greater immediately within and with-
out. The river is navigable for vessels of any
size, which are now for the most part taken up to
New Orleans by steam tow-boats, as the most
expeditious and economical method of reaching
the city. Sailing vessels seldom go farther up
than Natchez, 322 miles above New Orleans, as
the navigation of the river by steamboats is much
more convenient. The Delta of the Mississippi,
if we regard the efflux of the Atchafalaya as its
apex, and the Gulf of Mexico as its base, stretches
over two degrees of latitude and three degrees
of longitude. The distance from the outlet of
Atchafalaya to the mouths of the Mississippi is
220 miles. Its breadth varies from 10 miles to
100, and its area amounts to at least 12,000 square
miles, or one fourth part of the state of Louis-
iana. The very trifling elevation of the Delta,
by its acclivity from the ocean, is demonstrated
by the fact, that in autumn, when the rivers are
reduced to their lowest mark, the tides of the
gulf, of only about 2 feet mean elevation, are
sensibly felt in the Atchafalaya and Iberville, at
their efflux from the Mississippi, sometimes even
causing the current to flow back from the former
into the latter. Erom the physical characteristics
of the Delta, it has been supposed by some ge-
ographers that the main channel of the Missis-
sippi is changeable. But this must be a mistaken
opinion. When the annual inundations occur,
the surface of the river is indeed above that of
the surrounding country; and the effect of the
action of its powerful current in leaving a greater
deposit of alluvion upon its immediate banks
than farther back, has been to give them a per-
manent elevation above the general surface.
Nevertheless these superficial banks, which of
course are liable to accretion or abrasion in the
lapse of time, are as nothing to the deep bed of
the stream, which, as in the case of all other riv-
ers, is the deepest valley of the region through
which it flows. That this is the character of the
main channel of the Mississippi is apparent from
the soundings which have been made, showing a
depth at the head of the Delta, at the lowest
water, of 75 to 80 feet; of 130 feet near the out-
let of La Eourche, at Donaldsonville; of 100
feet and upwards opposite New Orleans ; and of
75 to 80 feet 3 miles above the main bars, at
its mouth. Comparing these elements with
those of the deepest lake of La., Lake Ponchar-
train, the bottom of which is not more than 18
to 25 feet below the general level of the Delta,
the bed of the river is seen to be from 75 to 80
feet below the bottom of the lowest adjacent de-
pression. With the exception of some changes
which have been effected, both in and above the
Delta, by the cutting off of the necks of isthmuses,
formed originally by almost circular bendings
in the river, the current of the Mississippi is as
effectually and permanently confined to its chan-
nel as that of any other river. In this phenom-
enon, such lakes as that of Eausse Riviere, (Ealse
River,) of which there are some six or seven,
either formed or forming, have had their origin.
This fine lake, in the parish of Point Coupee.
172 miles above New Orleans, was once a bend
of the Mississippi. In or about the year 1714,
the change above described was effected, from
which both the names Eausse Riviere and Point
Coupee (Point Cut Off) are derived. By cutting
through this narrow neck of land, the Mississippi
shortened its course upwards of 30 miles. Near
the new channel the old bed was rapidly filled
with alluvion, but in all other parts it retained
its original form, and is now a lake, with a mar-
gin possessing the usual fertility of the river
banks, and occupied with farms and farm-houses.
Erom the extent of country drained by the Mis-
sissippi, it necessarily follows that its spring floods
are very great, and of very long continuance.
In a mean of ten years, it appears that the swell
commences on the Delta about the end of Eeb-
ruary, and continues rising to the middle of June,
when the waters begin to abate. This long and
gradual discharge is occasioned by three causes,
depending on the vast extent of the region from
which the floods descend: first, varieties of tem-
perature from a difference of latitude and an
increase of elevation ; second, contrariety of di-
rection in some of the streams which constitute
the sources of the river; third, the time required
for the waters of the Upper Mississippi, of the
Missouri, and of other distant regions, to traverse
the long distance from the sources to the mouths
of this mighty river. The difference of latitude
from the mouths to the remotest sources of the
Mississippi is about 20 degrees, and the relative
elevation not less than 5000 feet. These elements
combined would give a winter climate to the
sources of the Missouri or Mississippi, equal to
that of Labrador, in lat. 61°, on the Atlantic
coasf. Permanent snows cover the earth in win-
ter, over the Atlantic slope and Mississippi basin,
as low as lat. 31°, the waters from which, it is ob-
vious, cannot be simultaneously discharged. The
general course of the flood being S., the spring
advances in a reverse direction, and releases in
succession the waters of the lower valley, then
those of the Ohio, and last those of the Missis-
sippi proper and the Missouri. Rising in lat. 42°
to 50° N., and at an elevation of from 1200 to
5000 feet, the higher sources of the Mississippi
are locked in ice and snow long after summer
reigns on the Delta. Then the course of the
Missouri and Yellowstone Rivers is to the N. E.
at first, for 500 or 600 miles, from which circum-
stances, together with the slow movement of the
waters, it results that the waters of the upper