The Yazoo Democrat., 1850-08-15
Mem0ir on the Physics Of the IEissis'
sippi River.
ny CALEB 6 ToRsHEY, a. D., c

ny CALEB 1oRsHEY, 4. IT., c, 3.
/. Rat 81 Fall-Ffom the mouth ef the
river to point 400 miles up is tortuous chan
mel, isa distance in right line of anlY 40
miles, Its length IS double the right line dis
tance for 900 miles above New OrIe8n IT
may for practical purposes, be regarded tVic
the distance ofthe right line
2. The mean.deptEpof the rigsrat lHgil sga )
ter mark isnctmaferially differed It d ateBez,
from Carrollton, though nearly 800 niles a.
part. A section of the river at Carrolltan.
made at Carrollton, made at high water of
lS49s is I63, 260 square feet; and ct Nldaiia
(opposite NatcheZ,) the section il 167, 600 feet.
The bottom.ef uniform channel 400 miles np,
is ubouton.a level withtle bar It the Souths
West Pass. The ra:e of form is not uniform
| on the surfacc, but decreases in declivitY to-
Wards the Gulf, giving d curve Of inclinaiion.
Elprohably parabolicl to which the level is
d tangenf.at tho Balize The mean rate.6f de-
lcinution is l.s0 iaehes per mile, for tho first
| hundred niles, :. 90 inches the second hnn-
dfed, 2 30 inches for the third, and 357 fsr the
fourth hundred dmiles. Above this point have
no accurate data. but am inclined to think hat
the rate is net materially different, to the ups
per extreme of the delta above The mouth Of the
/ Ohio. These data relate to high water.
/ 3. TlIelnw water curve Of deelivitY has q
mean decent of "a inches per mile for the first
hnndred miles, and 30, es3 I.20 for the next
consecutive three hundred miles; making the
total difrence of level 2I.I feet from a point
teh.maes above Matches, to the BaIize.
A Iheserates are not uniform for short dis
/ tances, interrupted as the channel is By many
short bends which arrest the currents regular
i flow, and make series of comparative levels
and falls in the surface current The means
r tolofc - q - =
the channel, 25, %, l6, and 100 miles III
length, and are, Think, reliable. They are,
at least, the best data within my knowledge.
5. Depth of water.-W Within the 400 miles
treated, the depth of the river at hfuh water Is
not materially different Near Natchez, ]
found an extreme depth of lk9 feet, and<a like
ldepth has ,been found al several points in the
Iyieinity of New Orleans.
Que depth Of l57 feet Nas recently fonnS
near Srewdsbary, about ten miles above the
tcity. These are extreme cases When the
channel is distant from beth shores, 125 feet il
the usual maximum. a section made in fronl
lof Vidalia, half a mile below the Natchez fer.
Try, gave mean depth of SO. 5 feet, with max.
imum Of about $50; and like section Of lligh
water cLannel at Carrollton gave mean depth
Eof7l g feet The low water depth may be OBJ.
tainen by subtfacting the ange from the higI
water. At Vi7alia, range. is 15 feet; and d
Carrollton 10 Il. The mean depth ofthe low
water sections would then be a0.5feet and &c
6feet. And the sectional are as at low watcl
give l33,0l0 square feet for Carrollton, anl
l08,000 at yidalia.
8. The channel continues to maintain gfea
depth, down to a point very near the debouch
IRE. How near, know not, bat certainly be
gond Tie head of the passes. AT Fort jackson
! Il Is feet deep. and point midway dow
q the Sont Vest Pass was found IO2 feet.
-TheuniformitYs Of breadthin ia,
, channelis.a remarkable featare of the Mississi
: lppi river. A great number Of measurement
! made by myself. from the Balize to Galena
s. / 700 miles mp the river, 9 i've mean width
J including wide places in the bends Of abou
1000 yards; excluding those 500 wards: an
: the upper portion Of thIsis wider, including ex
panses produced by. bends and islands, thai
q 1000 yards; but excluding them, they are th
same. The addItionof the four great river
: below, make 40 increase Ia the breadth ef iii
river. The Missouri At Bonneville, 300mile
8 above its mouth; found q half q mile wide.
1T appears frouIsthess facts relating to th
width Of the Mississippi, that Il doHsnot folos
7 the law Of cenfuest streams, as given in th
/ Books. We shall have occasionto sec that i
lmany other features il isa river SUI gensfis.
~ o. tt0CtbY 9l tk9t = 81 bl1ttt tlE SUI
face velocity Of the river, j have esfablishe
3 p6rrellcl sights, transverse 70 Tie river, an
g with an assistant, with ono Of the atationt
!, timed haating driitsWood, % still days, at d
parts oftbe surface, estimafi fipg By the eye thei
{ distance from shore. This have done at a
o stages ofetile waters and derived the mean
eachset, to the number Of many hdndreas {
lohervaiions.
81. The result shows 4 mean siiriaee ealscit
at higl water Of 2 81 miles par hour, at Carr0ll
tton, aud 260 miles per hour az Eidalia; rel
!, pectigely. $50 and 3.e2 feet per second {
Etime. The one was derived from I76 obsefFa
items, and the other from 20 observations
low water at Carrollten, 4 ,45 miles per hour, 0
{ IL feet per second; ut Y idalia 81 miles pc
u hour, 9 25 feet per second
To- The mean velocity formean water. 4
B derived from thirty Year's ohserYations IS 2 9
niles per hour, or 2..93 feet per second.
IL. The mean velocity. .at various depths af
81 neteasily yobtained. Theirregu gularities Of boi
tom and sides in the ch innel, and their contir
lually shifting nature, give so many lateral an
: vertical directions to portions of the curren
IS very much to aqualize the current Qelocit,
s. at all depths. Besides. the lafgeness Of fh
lvoIuTne rendeE friction much less inauenti,
than is usually computed for huents.a Accol
: Idingly IN sounding, have found the Leaf
when thrown in great depth, to be drilled dow
streams as fast as the boat from which Il NJ
g tlTgwns Sc the my standings we're nade ve.
d ticnlly by letting the boat drift while the Ten
8 was descending.
have allowed with some hesitation, on
Z eightii Tor retardation from friction, which
III instead Of 10 per cent, tho rate usual
allowe6. This IS liberal allowance At hla
9. water, but at low water. il II small enough,
lr we shall probably see
te ~. ItisrepaaE bic that tie high water SCI
|e lions af Vldalia and Carrollton, 275 miles
81 part should be the s0ile; but lnneh more r
lie, that obserVa tons should hnpe give
S. precisely llle same mean Velocity, 2 $50 aI
28l miles Pc hour. j his is what Should hal