The semi-weekly messenger. [volume] (Wilmington, N.C.) 1897-1908, 1906-01-26
LIGHTHOUSE ON DIAMOND Shoals.

destination will be held IN place Dy
suitable anchors and cables. 1t VIII
Immediately be scuttled by pumping
water into the interior compartments,
and it will be only a matter of a few
hours before enough water Will lave
entered to sink it, 80 as to rest on the
sands in about twenty-four feet or wa
ter, leaving the top or deck at this
time about Sc feet o the surface
of the ocean. The difference in tide
at this location is only about two feet,
and the shoal at the location selected
for the lighthouse IN the four fathom
contour, covers in area about two miles
long and one mile wide and gradually
deepens on the seward side.
1t is proposed TO place the light
house some distance back from the
outer side of the shoals, n 1t VIII
therefore be protected from the I'M
broken force Of the ocean waves, in
times of storm, as they Will already
have broken more han half a mile
away from the lighthouse. The shoals
below the four fathom contour
extend over an area Of about six miles
by two miles and the location propos-
ed, as shown by studies OF the govern
ment maps made during h last fifty
years, show but slight alteration IN
depth, and no apparent change in loca-
ton. The plans of these shoals are
dotted in many places, showing where
wrecks of vessels have occurred and
| where many at the present day tell
| the terrible tale of this location, and
are as grave-stones in this graveyard
of the Atlantic, where so many lives
have been lost.
NH 1l~N~ of tho aoiCCnn with the
| additional weight from scuttling will
settle into the sand some few feet i'm
mediately, until the bottom rests Oh
| the surface of the sand some twenty
four feet below the surface Of the
water. Water ballast will then be
pumped into the tw%enty-four side
compartments above the sea level, and
the floor will be kept horizontal by
pumping more water into the wells on
one side than on the other in case OF
uneven settlement. 1t is then propos-
ed to sink the foundation caisson as
quickly as possible, by a combination
Of dredging and the compressed air pro-
cess. the dredging being done in and
through the central we'll or shaft, and
| the caisson being sunk as far as prac-
ticable by open dredging through this
we'll. This work will be preferably
done in the spring Of the year, as at
that time the prevailing winds are
from the shore and therefore the seas
do not run so high.
Some valuable information has
been obtained from sea captains and
others who are familiar with this To-
cation. by passing back and forth In
storm and calm. 1t is found by thell
report that there is an average season
of some three months, during which
time no great storm has ever been re-
corded. The fact of this CO 'sson be-
ing a self-contained structure in al
! it's parts and requirements and being
able to sink itself into the submerged
! sands, by drawing those sands within
itself, utilizing a part of this sane
to mix with the cement, that will Ijrn
it's concrete filling, and gradually sink
ing itself, is only in keeping with 9th
er great engineering feats of the day
The great mining dredgers of the west
which slowly wend their way by dig
ging their trench in front and film:
it behind and the great modern float
ting dry docks are somewhat illustra
tive.
EXCAVATION IN THE CAISSON.
After the caisson has been sunk a:
far as practicable by open dredsin:
and added weight of water and con
crete, the lower air chambers will b'
filled with compressed air to force GU
the water, and men will enter thes'
chambers and assist the hydraull
! dredging machinery in excavating Will
powerful water jets, shovels and spe
cial tools, to force the same towar'
the central tube, where the sand will
then be pumped upward and discharg
ed through the outer shell on the out
side of the caisson by electors or sam
pumps. If n solid material, wreck
age, for instance, should be ncoun
tered in the sands while sinking, it
proposed to work it in towards tn
central shaft, where it may be reinov
ed by a graphing dredge. Smaller CD
structiOns may be removed by diver
through the air locks provided for III
men.
While the dredging is being don
the work will be carried On as fast a
possible in filling the different cham
bers with concrete. The material, &c
ment, crushed stone, granite block
boulders, supplies, ETC., will be brougf
} to the caisson in lighters weather pei
hitting, and will be quickly taken o
board by the aid Of the steam hoistin
: engines and stored in the differe1
rooms to be used when required.
!, balance in weight will be preserve
between the increasing weight of tf
i, structure and the increasing buoyar
= cy of the surrounding water as ii
!, caisson sinks to it's final depth. Tt
: caisson may thus be temporarily bel
+ at about the same level, to f~acilita1
, certain details of the excavation or
2 may be made To more rapidly sin
! in the sand.
BUILDING THE FOUNDATION.
AS soon as the caisson has bee
e sunk to its proper depth, about
feet below the surface of the sand, tt
bottom being about so feet below t.
e surface of the water, the work Of 81
3 ing will be carried on as quickly {