The Pensacola journal. (Pensacola, Fla.) 1898-1985, 1908-01-05

{ their completion, has caused a ire
mendOus scour, and has already made
/ so TO 50 feet OF water in some places
where. at the beginning of the work.
the depth was but little over man.
head. To make the uniform contract
depth, there is STILL in several spots.
about ten feet of mud to be removed.
! 1t is expected that the high water due
! within d few weeks will sweep the re-
the beginning of next summer
Overcoming Of Great Difficulties.
Probably few walls ever have been
constructed under greater difficulties
than were these jetties. They are
made of willow, scantling, stone and
concrete. Although in some places
they are not six feet deep, and al
though their greatest depth Is barely
fifteen fee, they have cost So, 700, 600.
! Every material entering into their
construction has been brought from
distances varying from 100 to 500
miles me jetties have no founda-
ton, but rely for stability upon their
extremely broad bases, being from
100 to $50 feet wide at the bottom.
In contrast to this great width of
base the concrete Gaping which
forms the top OF the jetties is but a
few feet wide. The Gaping Is a sea
wall 10 feet high. and is the only
portion of the jetties not submerged.
The wall weighs between two and
three tons per lineal foot.
The submerged structure supporting
this mass OF concrete Is made almost
entirely of willow poles and brush.
With the aid of frame works of scant-
ling, the willows were formed into go
called mattresses; broad, fiat struc-
lures resembling bed mattresses in
form, each about two feet thick, 200
feet long and varying in width from
So to $50 feet. The mattresses were
sunk one above the other. with the
widest at the bottom and those above
uniformly diminishing in width as
they approached the surface. The top
most mattresses were uniformly 35
feet wide and on level with the sur
face of the water. Heavy broken
stone was spread evenly over the
mattresses to sink them, SO that a
layer of stone rests between each OF
those willow structures. The greatest
number of superimposed mattresses
was five.
Forces of Nature Forced to Assist.
The Mississippi has done some very
interesting work in addition TO scour-
ing out a channel. for it has made the
mattresses practically indestructible
to any normal agency of nature in this
region by burying them under hun
dreds of tons of sediment. Those de-
posits follow closely the contour of
the jetties. in conjunction with which
they form new banks of the river. The
only change likely to occur in the
jetties is their gradual sinking Such
sinking occurred TO the jetties along
south pass.
In the course of many years, new
bar may form by silt deposits in the
gulf in the new deep water beyond
the mouth of the ietties. and then the
remedy will be the extension of the
jetties a short distance further. The
rate of bar extension during nearly rs
years preceding the starting OF the jet
ties was between $50 and ESQ feet an
nually. and the deposits responsible
for this advance We're made when con-
ditions now greatly changed, favored
su accretions.
Part of the s6.o0o.o00 allotted
to making the channel is being
spent in safeguards several miles
above the ietties to prevent any
increase in the flow through
other large outlets from the
main river 10 the gulf This is be-
ing accomplished by placing stone
covered mattresses on the river bot