New Orleans Republican. [volume] (New Orleans, La) 1867-1878, 1874-05-10

whether diffuse or concentrated, though
the abrasions will be materially different.
Forces are never lost, though their tacliity
of transmission is greatest IN water anu
least in solids, such as the river bank. And
since these banks are composed OF material
brought and laid down where they lie oy
these very waters, moving at velocity OF
three feet per second, whenever the new
forces brought to bear by greater velocity
of wave or current attack these particles,
they displace them and carry them down
to lower lands.
Let us take AN example. The steamer
James Howard, of side wheel construction,
and with 1900 tons freight, passed up the
river at near mean high water gauge, at
CarrolltOn, 1875 teet three feet below maxi
mum. Her rate was about ten miles per
hour against current Of four miles per
hour, making a movement of her waves
ten and four miles, equal to fourteen miles.
The waves OF practical value were Oblique:
$50 to her course on each side, and could
be distinctly counted to about the fifteenth
wave. and 1 added five for the confused,
irregular waves that followed. Ten of
these waves we're nearly of the same height,
and were measured by their rise on rod
and drift log that did not break them.
These waves averaged about sixteen
inches of height at 300 feet behind the YES
sci, ana the remaining ten waves averaged
less thar half that height, say elk inches.
They were all delivered against the banks
with the velocity of the steamer plus the
rate OF the current, say fourteen miles per
hour, or twenty feet per second.
Without attempting to weigh this force
by computing its dynamics from these data,
we assume the tonnage of the steamer null
tiplied by her velocity gives the just prac-
tical result.
1t is probable that the Towards own
tonnage is more than half her load, and that
23O0 tons would DO the weight of boat and
cargo We have, then, 4,600,000 pounds
delivered against the banks of the river at
the rate OF ten miles per hour, equal to l4.6
feet per second.
Now. this force is repeated every length
the vessel travels; and taking her length at
800 feet Or 100 yards, the force is repeated
l7.60 times in every mile. Thus the violence
done to the banks and levees by one trip of
the James Howard is measured by 1900 900
pounds multiplied by LAG seconds multiplied
by IL .bO for each mile of her travel. The
aggregate force, then, that is abnormal, APP
piled by this steamer, amounts in foot
pounds to lis, POI, 500 pounds=6O, 900 tons.
These quantities are SO enormous as to
be unappreciable to the mind unless illus
trated by some familiar example.
A .levee of nine feet in height, by the re-
cent formula of Humphreys and Abbott,
with slopes of two and three to one, con-
tains 1900 cubic yards in every hundred
feet, and 5000 pounds to the cubic yard.
The 300 feet of levee, equal to the length of
the James Howard, would weigh 10. 300, 900;
the force thrown against the levee or bank
each trip by the passing boat would be
&c, l6O, 600. which divided BY two equals
"a, OSS,00O pounds, more than three times
the weight of the whole levee.
Owing to 1.-THE tenaoity of the soil and ma
terials of the banks of the river, these
banks do stand these forces, repeated fifty
times a day under modified forms, and still
they stand almost miraculously this fearful
servitude.
But this is wholly abnormal, and charge
able to the commerce Of the Mississippi val
ley.
COMMERCE OF THE MISSISSIPPI RIVER.
1t follows, from the conclusions of the
last pages, that the entire tonnage of the
river must be aggregated, in order to make
up the accounts of the levees against the
Western cOuntry's commerce.
We arc indebted to Judge w. M. Burwell,
secretary of the New Orleans Chamber of
Commerce, for the items relating to this
commerce woven into this report.