Year: 1876

TIE MISSISSIPPI JETTlES.


The Difficulties and Triumphs OF tho Work
as Performed by Captain Eads.


The greatest difficulty that had to be
solved in building the channel at the
mouth of the Mississippi river was how
to control the waters of the great river,
and SO compel them to cut out the
much needed channel. A hundred
cubic yards of flowing water, spread
over watercourse Of one hundred
yards wide, would give only a yard of
depth. The problem was, speaking
relatively, to confne that one hundred
cubic Yards into channel which should
compel it to scoop out a deep channel.
Masonry had been used at the mouth of
the Danube, but masonry for such gigan-
tic work would far exceed in expense any
possibility that was within the powers
of the engineer of the Mississippi. At
this juncture some one suggested that
willows had been used to direct the
course of streams and to confne their
channels. Captain Eads and Colonel
Andrews consulted, and the result was
that they hit upon a plan for utilizing
the willows which CROWN great thickets
on the alluvial soil of the Delta to help
them in their work. On bar, or rather
island, which came into existence in the
river forty years ago in front of a
crevasse known as the "Jump," there
is willow thicket covering some thirty
square miles of land. Here was the ma
terial if it could only be utilized. After
long and anxious discussion, plan was
agreed upon and patented in the names
of the inventors by which willow mat
tresses were brought into use.


The mode of construction and subse-
quent handling of these mattresses is
particularly ingenious. On the bank of
the pass there is, first of all, constructed
a "launch way" consisting of lumber
built inclined platform, six feet above
the level to the landward and gradually
sliding down to the waters edge. On
the platform are two ribbands of well
creased pine which serve as the "ways,"
to use shipwrights' parlance. On these
ways are laid, first of all, strips of pine,
three by six inches in dimensions and
five feet apart, till the total width re-
quired is reached. These strips are
pieced on end till total length of about
one hundred feet is achieved. The num-
ber of strips is determined by the re-
quired width of the mattresses, which
vary, according to circumstances, from
fifteen to fifty feet. The strips being
placed in position, q number Of holes
are bored in each, into which are insert
ed hickory pegs atshort intervals, which,
when bolted in with oak wedges, stand
out thirty inches from the platform. On
the foundation thus made are laid the
willows; the first layer is laid crosswise
of the strips for about six inches, and
then lengthwise, and so on the layers
keep alternating till the tops of the pegs
are covered. When this point is reached
other strips are laid crosswise on the
whole mass, in which holes correspond
ing to the hickory pegs have been
bored.


Then, each peg having been fitted to
the superintendent hole, powerful lev
erage is brought to bear and the bind
ing cross strips are forced down on to
the pegs and securely bolted with oak
wedges. This completes the manufac-
ture of the mattress, which is then slid
down from the "ways" and foated on
to the water. A steam tug then takes
the floating mass in tow, and tugs it to
the position where it is to be sunk. The
mattresses vary in width from fifty to
fifteen feet, and supposing depth of
twenty feet has to be filed up, ten Of
the mattresses are sunk in the spot, the
lower one being of full width and the
upper ones graduating down to the
minor dimensions, each of them being
about two feet in thickness and hun
dred feet long. In placing them in po-
sition they are first foated on the spot
and attached to guide posts, when
stone barge is towed alongside and rocks
thrown on the mattress till it sinks. In
this manner the jetty is made. An al
ternate layer of willow mattress and
rock, broad at the base and gradually
narrowing toward the top, makes wall
which is impregnable to the assaults OF
the water, and so, as the jetties stretch
out, the current becomes confined and
1GS 1OICe COuceuGrdtSu. NO5 Ouly ID euo
stream thus deepened, but by curious
reflex action the ietty walls are strength
ened.


The ittoral current of the gulf runs
from west to east, and the debris thrust
out into the gulf by the concentrated
stream, being caught by the littoral cur
rent, becomes filled up on the outside of
the westward jetty, making firm wall
against all the inroads of the sea. So
marked is this effect that in the bay to
the west of the south pass, where year
ago steamer drawing nine feet of water
would move with ease, now skiff would
be grounded at high tide. The present
indications are that the commerce be-
tween the Mississippi valley and Europe
will pass through the mouth of the Miss
issippi inside the next twelve months,
and if the same mattress system can be
adopted for the river generally, depth
of water sufficient to carry heavy ton
mage can be made permanent between
st. Louis and the gulf.


Fortunes Freaks.


Postmaster-General Jewell recently