Savannah morning news. [volume] (Savannah) 1868-1887, 1885-11-23
THH CHARLEsrON JETTIEs.
An AnSwer to an Article in the New Or
leans Times Democrat OF Oct. 6.


ties Criticised. A review of them as
planned by Gen. Gilmore. Their faults
OF construction pointed out-why they
have not accomplished the object tor
which they were intended"
Press OF other more important work mas
prevented me from answering Als arucle
before. Unlike many critics OF the gov
eminent engineers, 80, ~ ADOPTS gen
orally avery moderate Tone, ana Ihe spirit
OF the article is apparently one OF I'M
preiudiced candor. II the facts upon
which so. Z. O." bases his reasoning
were correct. the conclusions he draws
might be difficult 10 disprove. 1t Is I'M
fortunate that one who writes with so
much apparent familiarity with the sub
ject should be so sadly IN error as TO what
IL ia proposed to DO, what mas been done,
what the estimated cost is, and what the
effects so far have been.
The title is misleading. .. T. Q. has
failed entirely TO state the reason why the
ietties have not accomplished the object
for which thew were intended. The rea-
son is plain: So 000OO0 is the estimated
cost; less than 81 ,30O. 900 have been appro-
priated; naturally the works are not yet
in sufficiently advanced state to Justify
any reasonable expectations OF pro-
nOunced results.
"A.-FILLING THE HARBOR."
Under head ga" 0. p. Q. states in the
most positive way what would occur II
the tide could enter only between the
outer ends of the ietties, and speaks OF
slope OF one foot to the mile as being that
which ia available to nil the harbOr under
this supposed case Of ietties, high through
out their whole extent. such slope as
this or anything experimenting thereto
would give velocities between the Jettles
dangerous to navigation.
1t is exceedingly difficult for an ordi-
nary mind to follow Q. p. Q.'s reasoning,
when he says: ''If Gen Gillmore's chan
mel could be realized between the outer
ends Of his jetties the incoming tide would
flow so rapidly between them that there
would be nut little influx over their low
inner ends" (What argument does o. p.
Q. find in this. fer raising the low inner
ends?) "ButAo much Of the ebb would
escape over the low inner ends that the
securing power OF the outward current
between their outer ends would be great
ly weakened, although the harbor might
be filled at each tide" Suppose it is
weakened, which we do not grant, the
deep channel has been already obtained
according to the superstition, and we can
well afford to dispense with superiluous
yelOcities.)
Why the food tide should flow with this
great rapidity through the jetty channel,
and not tend rather To follow as now the
general directions of the shores of Sulli-
vans and Morris islands is not stated.
As to the ebb tide, water tends to continue
to move in the direction in which it has
once acquired velocity. The shape of the
whole inner harbOr basin starts the con-
tanned water, flowing in the direction Of
Swash Getty channel during the ebb
tide. If there be deep channel in this
direction, as has been assumed by o. p.
O., it is hard to see why his ebb tide should
prefer turning aside and climbing over
jetties from 10 to 20 feet above the natural
bottom, to flowing through this easy,
short, and straight channel provided for it
in the direction in which it is already 60
ing.
1t is, Moreover, true that the drift from
Charleston harbOr goes out Of the Swash
channel or to the nOrthward of it. The
largest portion of the water going out at
ebb tide, formerly went through the main
ship channel. II however, this channel
Is reduced at the jetty to ten feet in depth
at low water, as it will be if necessary, it
is surely reasonable to suppose that with
a tendency already toward the Swash
channel as shown by the direction taken
by the drift, the greater portion of the
water will be diverted towards that chan
mel, and will pass out between the jetties.
1t is possible that with such slight
depth as ten feet, more water than is nee
essary to secure deep channel, might be
thrown thus through Swash channel, and
for this reason the final height of the
inner portions of the jetties has not been
fixed definitely. They will be raised just
high enough to produce the desired depths
and no higher. And this height can be
determined only by actual experience.
l am willing to grant, o. Z. O., that the
low inner portions of the jettles may not
be a necessity; that the water with suf-
heienC depth might come in between the
outer ends Of the jetties, and that high
jetties, properly located as such, might
give good channel, but will he please
explain wherein the necessity for high
jetties exists, if low jetties, costing one
third as much by his own admission, will
do the work. 1t does not appear from
anything which he says in section "a"
or elsewhere that they VIII not be effec.
tive. On the contrary, the fact that in
their present unfinished condition they
have produced considerable effects in
deepening the water on Swash reef aud
Jim Evans shoals, widening the present
channel, but without giving it any greater
central depth, is an Indication that, when
raised as projected they will do all that Is
demanded Of them.
o. =. @. is right in saying there are no
examples in the world of ietties built as
the Charleston jetties We're, designed by
Gen. Gilmore" In this connection It
may be we'll 10 quote l.. +. Vernon Har-
court, NJ. A., NJ. Inst, c. T., probably as
high a living authority as there is on har-
Dor works, who speaks Of the projected
harbor at Charleston as being "the finest
jetty harbor in the world" Important
advances in engineering science have al
ways been made in spite OF the strenuous
opposition and denunciatiOn o. conserva-
tive engineers. In proof OF this assertion
the SueZ canal, the foundations OF the st.
Louis Bridge. the blasting Of Hallets
Point, New York harbOr, ard score OF
other important aud successful works
may be cited. All these works were at
the time OF their conception as novel as
are any features Of the Charleston letties
at the present day.
"B,-THE BAR AND BAR ADVANCE"
Our critic dismisses with a very few
words the most serious question in con-
necti0n with any plan for improving
Charleston harbor by jetties. The litoral
currents upon which he relies TO "sweep
away the material" brought out from be-
tween the jetties. do not exist. There are
weak and variable currents due 10 wind
aud waves. but their direction is con-
stantly changing, and they cannot be re.
lied upon 10 remove large deposits. 1t Is
true that there is "A general tendency Of
the bar to move towards the west, which
is sufficiently marked 10 make 10 probable
that the relatively small amount OF mate
raasIN L.. i