The Canton mail. [volume] (Canton, Miss.) 18??-1882, 1876-06-10
THE JETTIES.

JOSEPH BARBIERE.
THE JETTIEs.
From the head of the jetties looking
seward down the Pass, one sees two long
double lines of piles, stretching out in
parallel lines to the crest of the bar.
From East Point the east jetty extends
| twelve thousand one hundred feet. The
west bank slopes off to the southwest.
On this bank, at point some four thou
sand feet further out than the head of
the east jetty, and sixteen hundred feet
from that line, the east jetty begins. 1t
extends about six hundred feet in a line
approaching the east jetty and perpen-
dicular to it, and then turns at right an
giles and runs parallel with it.
The two lines then run parallel out to
the bar, at a uniform distance of one
thousand feet apart. The direction is
almost perfectly straight, until within
about three thousand feet of the bar the
line curves slightly toward the south
west. The jetties extend now SO far out
as to embrace the crest of the bar. For
a considerable portion of the distance,
however, they have not been completed
to the water line, and at high tide a large
proportion of the water escapes from the
artificial channel. The work of filling
them up to the proper height is rapidly
progressing, however, the immense will
low mattresses Icing towed from East
Point and sunk with heavy stones upon
those already located.
The mud deposit accumulates rapidly
upon the mattresses in position, render
ing them every day more fixed and sub
stantial. Thus an immense solid wall is
being formed on each side, which it is
believed will be hardly less enduring
than the natural banks of the river.
The artificial bank appears also to be
assisted by nature in another important
particular. This is in the shoaling up
of the bay outside, against the jetty
work. Coming up the channel, Captain
Eads pointed out a mud bank just out
side of the west jetty, which was above
water at low tide, where some months
since there had been ten feet of water.
The length of one or both of the jetties
may be yet extended few hundred feet,
but probably not until the results of the
work already done shall have had suffi-
Gent time to develop more fully.
At the commencement of the work, the
little tugboat engaged in towing the mat
tresses was frequently grounding in seven
and half and eight feet of water-she
had to feel her way over the shallow
bottom. One day last January Capt
Eads' steam yacht, the Julia, bumped on
the crest of the bar in seven and half
feet of water. The soundings taken at
high tide on the 18th of May, 1876,
showed channel giving from fifteen to
eighteen feet of water over this crest, and
extending to eighteen, twenty, twenty
five, and sometimes thirty feet, higher up.
The passage of the Hudson, drawing
fourteen and half feet of water, on the
afternoon of the 18th, was made over this
same ground. She crossed the bar on
falling tide and steamed up the jetties at
a fair rate of speed, over course which,
for more than mile had not averaged
eight leet deep year ago.
Capt. Eads' theory that the securing
out process, resulting from the concen-
tration of the current within the chan
mel would begin from above, the mate
rial being taken up and carried forward
in suspension, appears to be fully demon
strated. The stream is making for itself
a bed sufficiently large to accommodate
the volume of water, and being confined
within fixed limits, Oh either side, en-
larges the section by deepening the bed.
The swift current pushes its way down
toward the Gulf, burrowing here and
there, and washing out deep holes and
channels in the material offering the least
resistance. Where it finds a hard spot,
surrounded by more yielding material
it naturally attacks and removes the
softer earth first, rushing around the
harder body and forming deep whirling
eddies about it, and gradually washing
it away. While this process is going on
the bottom surface is necessarily broken
and irregular, and frequently changing.
Where, for instance, the soundings show
an average of sixteen to eighteen feet,
the lead occasionally rests on a hard
bump or boulder, reducing the depth of
two or three feet.
Capt. Eads thinks that this Irregular
ity will necessarily continue for come
time, though with constantly deepen
ing tendency, until the current shall
have made for itself channel of width
and depth proportionate to the river
channel above. The velocity of the cur
rent will soon be further increased by
the building up of the jetty ends above
the water mark and by the gradual clos
ing of Grand Bayou, which will add
twenty-five or thirty per cent. to the
volume of water.
What becomes of the material which
is being washed out and carried away in
such quantities? Capt. Eads thinks it
is carried westward and dispersed over
the bottom of the gulf. Whether it is
producing any effect upon the sOundings
adjacent to the jetty mouths will proba-
bly, be officially known in short time,
upon the publication of the report of
the United States coast survey. Gen.
Comstock. of the United States Engin-
Ger Corps, has also been engaged in ex-
amining the results of the work, and