Chapter 15: 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.