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Show -- A STRANDLD 6ttIP AS a general rule a ship which has been badly damaged and sunk is not worth raising. It would probably cost more to raise her and repair her than to build a new ship. Her value as old iron, on the other hand, would not pay for raising and breaking up. She may, however, be in the way of other ships, a danger to navigation generally, and then she Is sometimes blown to pieces by a judiciously judi-ciously placed charge of dynamite. It Is usually worth while, however, to save parts of a wreck. If by any means they can be got at. Brass work, for example, is of sufficient value to be worth getting, and, of course, if gold or sliver either In the form of coins or bars be a part of the cargo, then it Is certainly worth an attempt. Sometimes even that is Impossible, because of the depth at which the wreck lies. As a diver descends the water pressure Increases, and to keep him from being crushed by It the pressure pres-sure of air In his dress has to be increased in-creased to the same extent, and there Is a limit to the amount of air pressure pres-sure which a man can stand. The main trouble Is that his blood becomes aerated under the pressure. Its condition becomes like that of oda water in a corked bottle, and as soon as he commences to ascend and the pressure Is reduced It becomes like soda water with the cork out. The nitrogen which was forced Into It by the pressure comes bubbling out as the pressure falls, and If this be allowed to occur too vigorously it will result In the diver's death. About thirty-five fathoms Is the limit below which man cannot go, and even at that, if the diver has to stay down any lengthof time, he must ascend again by easy stages with long Intervals of rest for his blood to get rid of the absorbed air; so that his ascent will take as much as four hours. Four hours spent In coming to the surface after but one hour's work below five or more hours' wages for one hour's work to an expensive ex-pensive man like a diver, to say nothing noth-ing of the wages of his attendants makes deep water diving an expensive matter, and beyond the limit mentioned men-tioned is out of the question altogether. alto-gether. Diving In Strong Currents. Then there Is the trouble caused by strong tides and undercurrents. The diver when in the water is the plaything play-thing of the currents. Robert Louis Stevenson, who once ventured on a diving expedition, describes himself as being "blown sideways like a leaf when In the water. Even large, heavy bodies like ships of iron are sometimes some-times carried to long distances by the currents. It Is said that the naval authorities have taus lost entirely an old submarine which they sank for the purpose of trying salvage experiments. experi-ments. They knew the spot where It went down, but when they tried to salve It It was not there. The under current had carried it away. It Is obvious, therefore, that diving in places where tide or current runs strongly Is very difficult And most salvage operations depend entirely upon the diver. Suppose that a ship is sunk in collision. He first goes down and examines the wreck. Upon his report it is decided whether it is worth while to attempt to salve the ship as a whole. It not, he may be told to salve the brass fittings, so down be will go again and again, with tools suitable for the work and will remove from the ship and send up all that he can procure that Is worth saving. If there be treasure on board he is the man who will have to get it H may be able to make his way to the place where it Is kept by the ordinary means, but sometimes he will have to blast holes In the vessel's hull In order to obtain access to It. Hundreds of thousands of pounds have been fetched from the sea in this manner, Sometimes there are among the cargo car-go things which are worth saving, and the diver has to get them out by similar methods. If the whole wreck Is to be saved, he has even more difficult feats to perform. For example, a very common com-mon thing is to patch the shell of a ship. The great, jagged rent in her side. It may be, where the bow of another vessel has cut Into her, or which has been gashed open by a sharp rock, has to be prepared for the patch which Is to keep the water out Wonderful Feats In Salvage. Measurements have to be taken, from which the patch can be made, Bhaped so that it will fit nicely. Probably Prob-ably holes have to be drilled in the ship's skin all, be It remembered, under un-der the water and finally the patch has to be put in place and secured with bolts. Then, when the diver has done all that the water is pumped out and the ship floated. Of course in seme cases the diver's work may only be to fix or run ropes by which the vessel may be lifted, but often he has much skillful work to perform under the difficult conditions condi-tions of complete Immersion in water In a thick, clumsy dress and under an abnormal pressure of air. It is. Indeed, wonderful what salvage divers can do. There are, however, instances in which ships have been literally "fished "fish-ed up" from the depths to which divers could not descend. One which occurs to the writer was that of a small naval vessel sunk in collision off the south coast Two steam tugs held the ends of a long cable, and by slowly dragging It along the sea floor they caught the wreck and drew the cable under It Several cables were thus got in place, and then, being pulled tight at low water, the tide lifted the ships above and so lifted the wreck as well, whereupon it was towed into shallower shallow-er water. This operation being repeated re-peated at every tide, the wreck was at last beached. In one well known Instance of salvage a ship was literally cut in two, but the two halves were In good condition, and it was resolved to save them both. The divers put In a temporary tem-porary end of timber to each and so they were raised, taken to the nearest near-est shipyard and there joined together togeth-er again. The salvage of wrecks is a very difficult dif-ficult and daring business, but there are men who are expert at it and whose experience is so extensive that they seldom fall at a job which they once undertake. It is only fair to say, however, that they are much indebted in-debted to the splendid diver's equipment equip-ment which is now procurable, without with-out which much that they do would be quite impossible. |