Looming up before him like a phantom in the foggy light is the ship; and now, perhaps, if any of the crew have gone down with her, the diver feels a momentary horror; but if no one has been lost, he sets about his work, and hums a cheerful tune.
It may be that the vessel has settled low in the sand, that she is broken in two, or that the hole in her bottom can not be repaired. But we will suppose that the circumstances are favorable, that the sand is firm, and the hull in an easy position.
The diver signals to be hauled up, makes his report, and in his next descent he is accompanied by several others, who help him to drag massive chains of iron underneath the ship, at the bow, at the stern, and in the middle. This is a tedious and exhausting operation, which sometimes takes many days; and when it is completed, the pontoons are towed into position at each side of the ship.
The pontoons, simply described, are hollow floats. They are oblong, built of wood, and possess great buoyancy. Some of them are over a hundred feet long, eighteen feet wide, and fourteen feet deep; but their size, and the number of them used, depend on the length of the vessel that is to be raised. Circular tubes, or wells, extend through them; and when the chains are secured underneath the ship, the ends are inserted in these wells by the divers, and drawn up through them by hydraulic power. The chains thus form a series of loops like the common swing of the playground, in which the ship rests; and as they are shortened in being drawn up through the wells, the ship lifts. The ship lifts if all be well—if the chains do not part, or some other accident occur; but the wreckers need great patience, and sometimes they see the labor of weeks undone in a minute.
We are presupposing success, however, and instead of sinking or capsizing, the ship appears above the bubbling water, and between the pontoons, which groan and tremble with her weight.
As soon as her decks are above water, so much of the cargo is removed as is necessary to enable the divers to reach the broken part of the hull, which they patch with boards and canvas if she is built of wood, or with iron plates if she is of iron. This is the most perilous part of the diver's work, as there are so many projections upon which his air-tube may catch; but he finds it almost as easy to ply his hammer and drill in making repairs under water as on shore.
The ship is next pumped out, and borne between the pontoons by powerful tugs to the nearest dry-dock, where all the damages are finally repaired, and in a month or two she is once more afloat, with nothing to indicate her narrow escape.