The Port Gibson herald, and correspondent., 1850-08-23


renders friction much less influential than is u.s.
ually computed for fuents. Accordingly, in
sounding, have found the lead when thrown in
great depths; to be drifted down stream, as fast
as the boat from which it was thrown. so that
my soundings were made vertically, by letting
the boat drift while the lead was descending
lhave allowed, with some hesitation, ,one-eighth
for retardaton from friction, which is l24 instead
of Is per cent, the rate usually allowed. This
is a liberal allowance at high water, but at low
water, lis small enough, as we shall probably see.
-. 1t is remarkable that the high water sec.
tions at Vidalia and CarroIlton, 275 miles apart,
should be the same; but much more remarkable,
that observations should have given so precisely
the same mean velocity, 2.60 and 26l miles per
hour. This is what should have been expected
from observations !ot the utmost exactness on the
hypothesis assume, that the Atchafalaya La
fourche. and Plaquemine carry off as much as
Red river introduces. :.
Is. Rise and Fail Of the Rirer.-The range Of
the river is, at Vidaia, as above stated 81, feet;
and at Carrolton Is feet These are the ex-
tremes not often reached. In 1929 and in 1919
the river was 81 feet below the mark of 1928,
and this latter mark is the highest for thirty
years, al all known points on the river, up to the
year l849, when the water reached in several
places the same point as in 1928. In 1915 the
water rose at Vidalia two inches higher than in
1928, and was said to be the highest water since
l770 Mr. Hutchings thinks the water mark
was made in ITO, which was still visible in his
recollection, fully one foot higher than any mark
since reached. Governor Sergeant records this
tradition, in 1909, when there was flood high
er than the forty years. The accompanying ta-
Bile or scale, l., will show the relative hight in
different years for forty years, and the date OF
elimination. These are from register kept of
actual rise and fall for thirty years, and from
other sources reliable. The range of high wa
ter marks is three feet at tCarrollton-1839, April
8th-the highest water of the year being three
feet four inches below high water. Low water
marks have much greater range; the lowest
mark of 1874 being seven feet above the lowest
known.
A. The Meridian line or curve Of rise and fall
for thirty years, 1917 to l847, reached an eleva-
tion just one foot seveninches below the mark Of
l849 This is in the last week Of April, which
proves to be the mean time of highest water.
The lowest water by the same mean il on the
lst o October, ald is three feet six inches above
the lowest mark. 1t will be observed that this
table has been reduced to Carrollton, or l5 feet
range in srise and fall; but the dates have not
been altered. They should be reckoned week
ten days later for Carrollton than for Vadalia.
The mean hight of this line for the whole thirty
years is 1922 feet below highest mark.
l5. Recapitulation- have shown the "rate
of fall, depth, breadth, velocity, and rise and
fall Of the water. From these we may compute
the rate OF discharge at all stages. and the mean
rate for thirty years. And the quantity by these
data, is l2,250, ,OO0,O 600, cubic feet per an
mum, or 447, SO cubic feet per second.
1t is worthy of especial observation, that the
mean for the three sets of ten years shows a
lower level of discharge at each consecutive Ten.
is. Sediment The experiments of Professor
] l.. Riddle show the sedimentary matter trans
ported by the Mississippi to bear portion in
bulk TO the whole quantity discharged Of one to
three thousand. At this rate, the cubic contents
would be- BY my measurements, as above, equal
to 4,082, ,333, 1873 cubic feet. The sediment, then
would cover twelve miles square ore foot deep.