Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-02-23

Difficulty of Getting More Than
Eighty Feet Below the Surface.
From the Marine Engineer.
The subject of raising submerged wrecks
Is most interesting one, though the prac-
ticability of such operations seems as yet
to be limited to depths of about $50 to zoo
feet and even at that limit there are few div
ers who can stand the heavy pressure.
About 60 to so feet seems to be the limit
at which divers can work for any length OF
time without an undue risk of hfe H. M.
S. Victoria lies. 1t is said. in about seventy
four fathoms of water, so there appel rs
to be but little probability that any at
tempts will be made to raise her, her
gigantic mass being also a serious draw
back to such salvng operations. Thomas
W. WALES has communicated a good deal
of interesting information on the subject
in a paper read before the Institute of
Marine Engineers at Cardiff. He gives de-
tails of experience of lifting vessels with
lighters and pontoons. The pontoons or
lighters must have sufficient buoyancy 10
exceed the weight of the submerged YES
sell and the pontoons and lighters are
brought to the submerged vessel at low
water, and large chain or wire cables OF
sufficient number and strength are passed
under the wreck and adjusted into position
with the aid of tugs and steam winches.
Generally divers are necessary 10 assist
in passing the cables under the snip. ana,
on Mr. AisbttS authority, 1t seems that
sc metimes considerable damage is done to
the salved vessels by the cutting into her
plating of the chains and cables unless
their strain is carefully distributed over
the surface of the plating and over the
hull of the vessel. AS the tide rises ana
the wreck is thus lifted it is towed toward
the shore until 1t is teached high and dry,
when any holes can be convenfently closed
and the wreck floated and locked. This.
however, describes an operation of salvage
where the position, size and condition OF
the wreck are easily dealt with.
xesdsi bottom which
cannot be closed by divers, platforming Is
often used a method of raising. This
method in particular requires the closest
given to raise the wreck but also that she
shall float upright and with SUFFICIENT free
board to be towed into safety when raised,
or all the labor may be thrown away by
have to be designed and placed to suit the
circumstances of the particular cases.
Sometimes they are laid diagonally within
four feet of the deck beams atdone end
and a, dip Of twelve feet at the. other.
Sometimes they must be laid higher at one
side than the other, and unless the'internal
weight OF cargo is adjusted accordingly,
this may cause the vessel to turn turtle
when she floats. The support of the plat
form to the hull or deck of the vessel must
be carefully thought out for If wreck
be a large ngle-decked vessel the whole
of the platform strain must not be taken
on this deck. Diagonal chains may be
used to tie the hatch coamingS and beams
to the ships frames to strengthen such
deck. Each division of the platform should
have a scuttling hatch to allow the reced-
ing tide to escape, or the air from the
under side of the platform with rising
tide. An air pipe should be fitted to each
division and carried higher up above deck,
ard iron bulkheads are not reliable for
water-tight platform ends. as they are apt
to spring away from the platform end and
admit water.
The closing of holes in the bottom or
sides of a sunken wreck is often q most
difficult job. and Mr.. Wales gives a most
interesting case Of a hole successfully
closed where it could not be got at in the
ordinary way. The steamer, coal laden,
had sunk on a soft bed of mud reaching
to within eighteen inches of her deck and
so soft that it appeared impossible to cut
through 1t or to keep 1t out even with
timbering and pumping, nor could the hole
be got at from the inside, as the mud
would flow in. Large steel plates, well
padded with canvas and hair felt and we'll
Quilted. were driven down through the
mud close to the hull, the plates overlapping
one another to make joint. and chains from
ring bolts at each end of the plates were
brought through the hull to winches to
draw the plates up tight as the water
was pumped out from the hold. Above the
plates on the hole the space was planked
over to the top Of the bulwarks and caulk-
ed tight. AS the tide rose about three
feet above deck level the vessel suddenly
f1oated, and the patching was found per-
fectly water-tight.