New-York tribune., 1879-03-29
THE MISSISSIPPI JETTIES.
CAPTAIN FAD9s GREAT WORK.

NEW-ORLEANS.
tFPoN AsPECIAL CORRESPONDENT OF THE rRTBUNE.l
PoRr EAps. La. March 1.-The readers of THE
TRIBUNE will perhaps remember a letter which ap-
peared in its columns in April. 1877, descriptive OF
the progress of Captain Eadss great engineering
work at the mouth of the Mississippi At the time
that letter was written the enterprise was still IN
an experimental stage. and many experienced engl-
neers doubted its final success. The river had been
harnesSed its current confined and accelerated ana
its waters forced to deepen the channel ana wear
nway the bar at the entrance TO South Pass. StlIl
il was argued by the sceptlcal that the walls oi
willow mattresses covered with broken stone would
soon be undermined and swept away and that
n new bar would speedily be formed outside
the etties and would become in few years as great
On obstacle as the old one. The pilots who nave
their homes at the Southwest Pass the greatest
croakcrs aud they persisted in bringing vessels IN
at that entrance and occasionally leaving them
stuck fast in the mud long after there was plenty
Of water at the jcttes. Most of the Army engineers
believed Captain Eads would fail aud the mer-
chants and shippers Of New-Orleans. who were VI
tally interested in his success, gave him little en-
couragement.
Visiting South Pass after lapse of nearly two
years find everything changed. All the shipping
now comes in at this entrance. Southwest Pass Is
abandoned, except by fishing smacks and few
coastng schOOners, and is of no more
value than the Belize which was given up
many years ago. The jetties stretch out
into the Gulf IN two long wave-washed lines, and
between them the turbd current of the great river
dashes far ont to sea, projecting its muddy waters
through the blue brine beyOnd the reach of the eye
Between the iettes there is a trustworthy depth of
twenty-three feet at average flood tide, ana heavily
laden ocean steamers of over 5000 tons burden
pass out and across the bar without lmpcdlment.
The Government dredges, which used TO be em-
ployed the year round at great expense
dredging the bar and the mud Jumps at
Southwest Pass, stopped work several months
ago the feet Of pilot-boats abandoned
that entrance. and South Pass Is for all the
purposes of commerce the only way of getting into
the Mississippi.
The work on the jetties is by no means completed,
however At the sea end of the two walls the ac-
tiOn of the waves has damaged some 600 wards of
the structure, and this misfortune has shown that
it is to make the walls rmer for the last
third of mile. To this end two tiers OF enormous
blocks of cement are being put on top of the
mattresses. The blocks of the lower tier are
16 feet long, feet thick and feet wide Those
of the upper tier are of the same length and thick
ness, but are only 3 feet wide. heavy expense
and much difficult labor involved IN this work.
First the broken stone is thrown off the top of the
mattress walls, and thick layer of small stones
and coarse gravel thrown on and worked down
between the willow twgs with crOwbars. Then
niles are driven and railway is constructed up in
the air about ten feet above the jetty. Stout
plank boxes are then placed on the jetty and the
cement is transported from the mixer IN an iron
car and dumped INTO the boxes, where 1t soon
hardens When il Is remembered that this
labor is all performed nearly two miles out at
sea on a narrow wall of willow twigs washed by
the waves at nigh tide, ITS arduOus character will
be appreciated. After the blocks are in posi-
ton slope of broken stone will he formed on the
sea side of the WALL aud the work Will then be fin
ished. 1t WILL of course, need repairs year by year.
but Congress has made a liberal provision for this
In its contract with the Jetty Company 1t is prob
able that portions of the structure Will grad
ually sink into the mnd, and will have to be main
tanned at the proper height by fresh layers of mat
tresses and stone.
Ihave spoken of the general features of the work
thus far in terms that presuppose that the reader has
already some knowledge of the plan and method of
construction. For the benefit of those to whom
the subject is unfamiliar let Inc interpolate an
explanatory paragraph Take yhIee-tined fork
bend two of the tines outward and split one at the
end and you will have pretty good representation
Of the enormous natural mud jetty which the MisSs-
sppi River has constructed in the OF centuries
and projected thirty miles out into the Gulf. The
right hand tine will be Southwest Pass the middle
one South Pass and the ends of the split tine Pass
apOntre and Northeast Pass. Imagine the handle
and tines to be mud banks covered with reeds and
elevated about six feet above the level OF the GuIf'
and that the river flows in deep
trough between these banks, and you Will
get notion of the peculiar topogra-
ply of the Mississippis mouth. The action which
formed these natural jettes still goes on. prolong-
ing them and depositing bars in the outside
their mouths Now, the plan Of Captain Eads was
to do in three OF four years what the river would
do in as many centures-DrolOng one OF the prongs
of the fork out TO the further edge of the bar by
80 dong he proposed to accelerate the current and
force the water to take up sediment instead OF de-
positinr IT, and thus deepen its own bed and scoop
out q channel over the bar. To prevent the forma-
tOn of new bar he depended on the htoTal cur
rents and if these did not suffice he knew that
new formation could not he troublesome Tor AT least
half century and that his jetties could be prolonged
if necessary. He chose the South Pass for ms eN-
pertinent, Orrather the Government restrctedhlmt 70
one of the three shallow unused passes. anu Woulu
not permit hun operate Southwest Pass Tor lear
he would spoil the only practicable entrance. SOuth
Pass had but feet OF water on us BAR ana was OF
no use to shipping. First be increased the amount
of water flowing into 1T by shutting up bayou that
led out of it and sinking line of mattresses across
the heads of the two other passes. "a mattress is
construction OF willow twigs and panks about
forty feet long fifteen wide and three thick and 1t
Is sunk by pIling stones on IT. lhen ne began MS
ietties from the ends OF tho mud banks Stragh OUT
into the Gulf sinking mattress top of another
until the wall thus madeappeared above the surface
and covering 1t with stones brought from
the Ohio River q distance of 200 miles. num-
Der of wing dams were thrown out at right angles
to the walls to narrow the channel and throw
greater volume OF water INTO The centre he WoIK
was begun in May, 1875, and will probably be
completed next Fall. Ii has had the prec Sc result
predicted by its protector thus far The channel is
now deep enough for all ordinary uses ana II thero
are any unsettled questions connected with the en-
terprise they the cost OF keeping the Jetes
IN. tl,s