The star. (Cincinnati [Ohio]) 1874-1875, 1875-05-31
THE JETTY system.

ITdCt Jne dtCeutioH OIL Lne engineering anu
commercial world. On Saturday he
made his first soundings with view to
commencing work, and we are informed
to-day by telegraph that he was fully
satisfied with the result of bis exami-
nations.
The plans are of especial interest to
engineers as solving the problem 30 long
considered OF the permanent connection
between the navigable bed Of the river at
and above New Orleans and the Gulf,
and of greater importance to the country
at large and the West in particular, In
opening to us in the South port which
shall be second to none on our coast.
The jetty system which he has decided
upon, is now fully recognized as sus
perior to the formerly considered canal
and harbor project, and already those
examining his plans and giving the mat.
ter their careful attention, predict a
complete success tor the enterprise.
Active preparations for commencing op-
erations are now making, as by the pro-
visions of the act work must be begun
during the present year, and as soon as
the summer months are passed the great
enterprise will doubtless be put under
way. The South Pass, as is well under
stood, is the one which it is proposed to
deepen. 1t is nearly thirteen miles long
and has minimum depth Of nearly thir-
ty feet and width of over seven hun
dred. At the mouth the swift, deep cur
rent changes into a broad, shallow
stream, spreading over very wide bed
and flowing much more slowly. o.. .'
The consequence is thar the quicksand
and sediment brought down from above
by the swift stream settles to the bot
tom as the current becomes more slug
gish, and large share of the $4,000, 600
cubic yards of matter which it is estima-
ted the stream annually brings down is
deposited on this bar, and navigation by
large vessels, which in other parts of
the stream would be practicable, is thus
rendered impossible. The current near
the banks being still less, the sediment
is deposited more rapidly, and the
waters forced into the middle at the
head of the bar. This causes small
portion of the upper part of the bar tobe
cut away by the current and deposited
still further down, so that the bar itself
gradually works further south at the
rate of about one hundred feet per year.
From the point where 80 feet of water
are found in the channel above the bar to
the same depth OF water below or out
side is distance of about 1900 feet.
There is, however, outside the bar a
shoal, where there are but II feet of
water. The bar at the mouth is covered
by but feet. The plan is to build 4
TWO parallel jetties or dykes over or
through this bar, so as to confine the
within narrow limits at this |
point, and by thus forcing a swifter ana
deeper current, cause it to not only
carry away the bar it has been forming,
but to keep open a channel Of the same
depth as that above, and thus give sufi-
cient depth of water for the passage of
ocean vessels up to the docks at New
The shoal outside will also
have to be deepened, but the action of
the swift current thus discharged upon
it will assist much in this work. and but
little dredging will be necessary.
The jetties will be $4,000 feet long, each
one being 10 feet wide on top at the up
per end, and 80 feet on top at the lower
OF outer end where they will be exposed
to the action of the waves. They will
of course be above high water mark, and
the foundation will be sunk sufficiently
low to prevent the river undermining
them. They will probably be built of
what are known among engineers as
"fascines." They are sort Of fbag-shaped
willow basket, which will be filled with
broken stones, and the faces of xhe wall
be built up of them and thf the'r part
filled in with stones and e6sIN They
will be thoroughly secured &sNeSl and
rods, and the interstices viii fraptSsly fill
with sediment from the river sS that
long before the willows have become
useless the wall will be perfectly solid.
The cost is to be S., ,259.000 which is to
be paid by Government only after the
work is completed, and the object fully
secured. The progress OF the delta into
the Gulf will necessitate a constant ex-
tension of the jetties, and s125,000 per
year has been provided for this and for
keeping the whole in repair. The work
IS to be carried on by Captain Eads at
his own expense, and if at the period Of
thirty months there is not navigable
depth of twenty feet in the channel the
contract is to be void. Should the work
be satisfactory half million will then
be paid, and like sum every time two
feet are added to the depth until it
reaches thirty feet. At the end Of ten
years, If the entire contract is completed,
one-half of the balance is to be paid and
ten years later the remainder, when the
Cove rnment will take charge Of the
works and maintain them at its own ex-
pense. What the result of this stupendu-
GUS work will be is only beginning to