Year: 1876




these can make, under favorable cir
cumstanees, about seven day. Mat
tresses cannot be kept; they must be
used as soon as made, and they must
be made of green willows. II kept
too long, or made of willows cut many
days, they require too much stone to
sink them. Ifput afioat they water
sob and sink, when green, in few
hours. When, therefore, the bar is
too rough to put down the mattresses
at the right spot, work must be sus-
pended in mattress making. All work
is paid for by the hour-night and
Sunday work included. The willows
compose the mattresses, the mattresses
one on and after others, compose the
jetties, and thus the little switches on
| the river bank have furnished the
most effectual means of curbing and
controlling the current of the great
Father of Waters.


When the mattress Is completed, as
1t must be used at once, powerful
tug comes alongside, stern on and TAX
ing hold of the hawsers previously
placed beneath, it pulls away until
the mattress glides easily of the slop-
ing way with one or two men on il,
and floating, it looks like raft of
brush.


The tug Immediately clearing her
stern lines takes it i'm tow and moves
out to the place designated for it, and
each mattress is made to fit its place.
If it is not too rough to put it in its
proper place, but If the bar is too
rough, then it Is made fast at some
point in the lines of jetties where, If
it cannot be removed before it sinks,
it will not be lost, but be in the next
best place.


Placing the mattresses is done by
towing ii to the inside of the line of
guide poles, making it fast to the pill
ing just over the spot where ii is to be
sunk. This is easily done in smooth
water, but is fearful operation in
rough weather, as wind, waves and a
fierce river current have all to be
struggled with.


The jetties when thoroughly CON-
pleted, will rise up from the bottom
like stair steps, with their back rest
ing against the piles on the inside of
the channel, and rising from the bot
tom by steps five feet wide and three
feet high, until clear above water
On the top, then, will be laid solid
pavement some fifteen feet wide, of
smooth stone, like one of our New
Orleans square block or Nicolson
pavements. 1t will be made smooth
and solid, to prevent the heavy seas
which will break over it from tear
ing it up or ripping off any of the
stone.


The interstices of the willows rapid
ly become filledwith Mississippi mud,
and will become solid banx The
mud of the Mississippi, it is well
known possesses a wonderful preser-
vative or anticeptic property for vege-
table matter,as the bluffs ut Port Hud-
son and the borings around New Or
leans show; even leaves, twigs and
acorn hulls are found well preserved.
it is the property of the river mud
that will make the jetties perinan-
ency when once put down.


To more thoroughly complete the
jetties, stone ballast will be thrown
on the five foot steps of the mattresses
on the channel side until they are
loaded fully, SO as to cause them to
sink or bend downward iato the chan
mel, as the current may scour next to
them.


A steady, constant and rapidly in
creasing debth along the whole slope
of the bar, and now thirteen feet of
water on the crown of the outer bar,
where heretofore, for nearly hun
dred years, there has been a debth of
seven anb a half to eight feet; and the
securing is SO rapid that the bar is
deepening two inches and a halfevery
day.


Every principle of the jetties, as an
nounced by Captain Eads and sustain
ed by Colonel Bayley and the consult
ing engineers, has been put to the test
and verified. AS these principles in
volve many laws ofhydrarlic, hydros-
tactic and hydrodynamic science, not
yet thoroughly known, it is needless
to discuss them in this article.


The effect of the jetties is all that
could be reasonably expected. 1t is
now simply question of time, more
or less brief, but certainly brief; the
work of erosion is going Oh rapidly
and surely, night and day; the river
takes no rest; the mighty current is
gnawing away at its prison gates. 1t
cannot gnaw its way out through the
thick walls along its sides; it cannot
turn backwards, and it is, therefore,
eating away at the soft and yielding
bottom with resistless erosion, and
throwing, with terrific force, the
securing far out into deep water.


The current has not only deepened
the bar far up the channel as was cal
culated but it is, now that it has been
concentrated, cutting the bar ut the
mouth of the jetties into holes. Col.
Andrews and myself sounded all
along the crest Of the main and outer
bar, and where the Coast Survey, a few
months ago, found 81 and u feet of
water, we sounded 8, 10, 10, 26 and y
feet holes all over the west portion of
outer bar. This shows that it is cut
ting into holes, leaving only hard
Jumps here and there.


But the most astonishing effect Of
the jetties, and one which puts at rest
one of the strongest arguments and
objections to the jetty system, is that
the scourings and fresh deposits from
top river have not been deposited
just at the mouth of the jetties, SO as
to necessitate u yearly extention of
jetties.


All matter held in sustention,
whether brought down with the pres
ent high water or secured from the in