APPARATUS FOR RAISING SUNKEN SHIPS AND TREASURE
It is somewhat curious that, while the sciences connected with the
building of ships have progressed with giant strides, little attention
has been paid to the art of raising vessels which have found watery
graves in comparatively shallow depths. The total shipping losses of a
single year make terrible reading, since they represent the extinction
of many brave sailors and the disappearance of huge masses of the
world's wealth. A life lost is lost for ever, but cargoes can be
recovered if not sunk in water deeper than 180 feet. Yet with all our
modern machinery the percentage of vessels raised from even shallow
depths is small.
There are practically only two methods of raising a foundered ship:
first, to caulk up all leaks and pump her dry; and secondly, to pass
cables under her, and lift her bodily by the aid of pontoons, or
"camels."
The second method is that more generally used, especially in the
estuaries of big rivers where there is a considerable tide. The
pontoons, having a united displacement greater than that of the vessel
to be raised, are brought over her at low tide. Divers pass under her
bottom huge steel cables, which are attached to the "camels." As
the tide flows the pontoons sink until they have displaced a weight
of water equal to that of the vessel, and then they begin to raise
her, and can be towed into shallower water, to repeat the process if
necessary next tide. As soon as the deck is above water the vessel may
be pumped empty, when all leaks have been stopped.
In water where there is no tide the natural lift must be replaced
by artificial power. Under such circumstances the salvage firms use
lighters provided with powerful winches, each able to lift up to 800
tons on huge steel cables nearly a foot in diameter. The winches can
be moved across a lighter, the cables falling perpendicularly, through
transverse wells almost dividing the lighter into separate lengths, so
as to get a direct pull. If the wreck has only half the displacement of
the lighters, the cables can be passed over rollers on the inner edges
of the pontoons, the weight of the raising vessel being counteracted by
water let into compartments in the outer side of the pontoons.
There are ten great salvage companies in the British Isles and Europe.
The best equipped of these is the Neptune Company, of Stockholm, which
has raised 1,500 vessels, worth over £5,000,000 sterling even in their
damaged condition, among them the ill-fated submarine "A1." Yet this
total represents but a small part of the wealth that has gone to the
bottom within a short distance of our coasts.
Turning from the salvage of wrecks to the salvage of precious metal and
bulky objects that are known to strew the sea-floor in many places,
we must notice the Hydroscope, the invention of Cavaliere Pino, an
Italian.
In 1702 there sank in Vigo Bay, on the north-west coast of Spain,
twenty-five galleons laden with treasure from America, as the result
of an attack by English and Dutch men-of-war. Gold representing
£28,000,000 was on those vessels. Down it went to the bottom, and there
it is still.
So rich a prize has naturally not failed to attract daring spirits,
among whom was Giuseppe Pino. This inventor has produced many devices,
the most notable among them the hydroscope, which may best be described
as a huge telescope for peering into the depths of the sea. A large
circular tank floats on the top of the water. From the centre of its
bottom hangs a series of tubes fitting one into the other, so that the
whole series can be shortened or lengthened at will. Through the tubes
a man can descend to the chamber at their lower extremity, in the sides
of which are twelve lenses specially made by Saint Gobain, of Paris,
which act as submarine telescopes.
Pino's hydroscope has been at work for some time in Vigo Bay, its
operations closely watched by a Spanish war vessel, which will exact 20
per cent. of all treasure recovered. While the hydroscope acts as an
eye, the lifting of an object is accomplished by attaching to it large
canvas bags furnished with air-tight internal rubber bladders. These
have air pumped into them till its pressure overcomes that of the water
outside, and the bag then rises like a cork, carrying its load with it.
An "elevator"--nine sacks fixed to one frame--will raise twenty-five to
thirty tons.
So far Cavaliere Pino has salvaged old Spanish guns, cannon-balls, and
pieces of valuable old wood; and presently he may alight on the specie
which is the main object of his search.
Another Spanish wreck, the _Florida_, which was a unit of the Spanish
Armada, and sank in Tobermory Bay, the Isle of Mull, has many times
been attacked by divers. The last attempt made to recover the treasure
which that ill-fated vessel was reputed to bear is that of the
steam lighter _Sealight_, which employed a very powerful sand pump
to suck up any objects which it might encounter on the sea-bottom.
Many interesting relics have been raised by the pumps and attendant
divers--coins, bones, jewels, timbers, cannon, muskets, pistols,
swords, and a compass, which is so constructed that pressure on the top
causes the legs to spread. One of the cannon, fifty-four inches long,
has a separate powder chamber, the shot and wad still in the gun, and
traces of powder in the chamber. It is curious that what we usually
consider so modern an invention as the breech-loading cannon should
be found side by side with stone balls. The heavier objects were, of
course, raised by divers. In this quest also the treasure deposit has
not yet been tapped.