[8] There are five more cliffs above this state, between it and the
mouth of the Ohio; and one on the western shore of the Mississippi at
Helena, Arkansas.
[9] The following extract from a private letter in the author's
possession, bearing date New Orleans 28th April, 1804, contains some
interesting facts, relative to the depth of the lower Mississippi, and
other characteristics of this river, which were obtained by the writer
from actual observation.
"In Nov. 1800, when there was scarcely any perceptible current, in
company with Mr. Benj. Morgan and Capt. Roger Crane, I set off from just
above the upper gate of this city and sounded the river, at every three
or four boats' length, until we landed opposite to M. Bernody's house on
the right bank of the river. The depth of water increased pretty
regularly; viz. 10, 12, 13, 15, 17, 19, and 20 fathoms. The greatest
depth was found at about 120 yards from Bernody's shore. This operation
was accurately performed; and as the river rises about twelve feet on an
average at this place, the depth at high water will be twenty two
fathoms. A M. Dervenge, whose father was chief pilot in the time of the
French, informed me that his father often told him that a little way
below the English Turn there was fifty fathoms of water; and M. Laveau
Trudo said that about the upper Plaquemine, there was sixty fathoms, or
three hundred and sixty feet.
In the year 1791, during five days that I lay at the Balize, I learned
from M. Demaron Trudo, who was then commandant of that place, that there
was about three feet difference between the high and low waters. From
the best information I have been able to collect, there is a declension
of eight or nine feet from the natural banks of the river at this city,
to the banks upon which is the site of the house where the Spanish
commandant lived before they removed up to Plaquemine, at the distance
of about three leagues from the sea. There is a gradual slope or descent
of the whole southern region of the Mississippi river, from the river
Yazoo, in lat. 32 deg. 30' N. to the ocean or Gulf of Mexico. The elevation
of the bluff at Natchez is about 200 feet; at St. Francisville, seventy
miles lower, it is a little more than 100 feet; at Baton Rouge, about
thirty miles lower, it is less than 40 feet, at New Orleans, according
to the above statement eight feet, and at the Balize less than two feet.
This vast glacis, at a similar angle of inclination, extends for some
leagues into the Gulf of Mexico, till lost in the natural bed of the
ocean.
The river, whose current is said to be the most rapid at the period when
it is about to overflow its banks, runs in its swiftest vein or portion
about five miles an hour. I allude to the line of upper current, and not
to the mass, which moves much slower than the surface. The average
velocity of the river when not in flood is not above two miles an hour.
This is easily ascertained, by the progression and regular motion of its
swells, and not by its apparent motion.
In November, 1800, as before observed, the motion of the stream was so
sluggish as to be scarcely perceptible. A vessel that then lay opposite
the Government House, advanced against it with a light breeze. I was
told by a respectable lady, Mdme. Robin, who lives about six leagues
below the city, that the water of the river was so brackish that she was
obliged to drink other water, and that there were an abundance of
porpoises, sharks, mullet, and other sea-fish, even above her
plantation, nearly one hundred miles from the Gulf. The citizens thought
the water brackish opposite the town. It looked quite green like
sea-water, and when held to the light was quite clear. Although I did
not think it brackish, I found it vapid and disagreeable. This is a
phenomenon of rare occurrence, and not satisfactorily accounted for."