The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1878-07-10
what Are the JeftSes s?-..Now's Your
Chance to Know.

Chance TO hnOW.
The following description OF the jetties
now in course of construction In the South
Pass Of the Mississippi river, under the SUI
peryision Of Captain Eads, appears in The
columns Of the Boston Traveller:
Where The Mississippi river empties into
the gull it divides itself into three passes.
the Southwest Pass, "a miles long, Low
feet wide, and having an average depth OF
10 feet; the South Pass, 10 miles long, oo9
feet wide, and having an average depth OF
81 feet: the Pass L'Outre, Il miles long,
400 feet wide, and having an average
dentb Of Is feet. Just above these passes
the river is 5000 feet wide and 80 feet deep,
which continues up to New Orleans, ITO
miles above. The South Pass, Wnere tie
ietties are to be constructed, eml,tles about
fen per cent. OF the whole amount OF the
sediment, and the three passes empty annu-
ally / ZOO, 900 cubic feet OF sediment into
the gulf.
Previous TO awarding the contract to Cap
tain Eads, OF st. Louis, the Government
endeavored to improve navigation by dredg
inc. which has cost annually S250,0O0.
Captain Eads proposed his plan, and It was
accented. He desired to work in the South
west Pass, but the Government Thought IL
best to try the South Pass, the middle and
smaller of the three. The total cost to the
Government will be S5,250,000
The construction and lodgment OF the jet
ties are, briefly, as follows: In the first
place, extending back from the banks OF the
river, at 4 slope OF one in ten, piles are
driven. There are three or more rows OF
these piles, and they are joined together by
heavy timbers. This. when finished, Is
called the stay-way. Now barge heavily
loaded with willows comes alongside the
stay-way, and the men throw number OF
| LAYERS OF these willows at right angles to
each other on the top OF the stay-way.
These layers are securely and tightly
bound together by thongs, making, when
finished, what is called willow mattress.
These mattresses are OF various dimen-
sions, generally some 400 feet long, forty
feet wide, and two feet thick, for reasons
which will be hereafter explained. When
the mattress is completed tug steamS up
alongside the inclined stay-way, and
hauling it off drags it to its position on
the ietties. These mattresses being made
OF willows will, OF course. float; few
inches only, however, remaining above
the surface of the water; and SO, when in
position, they are sunk by stone known
as "rip-rap," a very heavy limestone. which
is brought from the Ohio river. There are
number OF courses Of mattresses, each
course being narrower than the one imme-
diately below it; so that when viewed in
profile they have the likeness OF steps
ascending from the bottom OF the river
I'D to the banks. The lower course is
about 40 feet wide, the second about 50
feet, and the upper or top course about
25 feet wide. This constitutes 4 letty.
They are. OF course, built from the bank
out into the river, and great deal OF the
sediment is carried by the current in and
back Of the ietties, where it lodges. The
ietties are constructed also out into the
Gulf Of Mexico number OF feet so as to
enable the river-current to bear whatever 1t
may bring along with it out into the ceep
waters, where, in the first place, there is
less liability for it to settle, especially in the
form Of bar or in a narrow space; and
where, in the second place, ii it does set
tie, it can obstruct navigation but trifle.