PERILS OF DEEP-SEA DIVING

Dominion, Volume 19, Issue 119, 13 February 1926, Page 22

PERILS OF DEEP-SEA DIVING

CHANGES IN SEA PRESSURE

The dramatic salvage operations over the lost submarine Ml, direct attention to one of the most hazardous and exclusive occupations of man—that of the deep-sea diver. Yet, surrounded as he is bv exceptional perils, he is at the same time protected by extraordinary safeguards. A diver is more likely to lose his life by making an ascent from the bottom to the top of the water at too great a speed than from any of the sensational causes dear to the heart of the film producer, says a Home paper. After working at great depths, the diver must come up at a specified rate. Otherwise he falls an immediate victim to a form of paralysis known as caisson disease, due to the liberation of bubbles of free nitrogen m the blood as the result of too swift a change of pressure outside.

This disease is fatal if not treated diastically by immediately submerging the palsied diver again to a depth where the pressure of water is the same as that at which he had been working. Then he is brought back to the surface once more .it the right speed. Often an attendant is sent down with him.

Another way of effecting a cure is to place the afflicted man in a recompression chamber, where he is gradually subjected to a pressure equivalent to that where lie was working under water. This pressure is then reduced at the correct rate.

The rate of progress of a diver from deep water to the surface varies. A man working for 20 minutes at a depth of 200 ft. should take 67 minutes to come to the top. He must pause at various stages on his upward journey, and these pauses get longer the nearer he comes to the surface

Thus, at 70ft., he must stop for three minutes; while when 10ft. from the top he must pause for as long as twenty minutes. He can tell what his distance is at any moment from the feet or fathom markings on his life line. On the other hand, the diver can go down as quickly as the air supply from above will allow him. He soon knows when he is descending too rapidly, because he feels himself being “nipped” by the pressure of the water outside, water pressure without. In the German apparatus used in the Ml operations, the armour of the diver bv itself withstands the pressure of the water, the air inside the suit being at normal pressure all the time, just as in a submarine. A diver encased in this armour comes up or goes down as rapidlv as he wishes. There are onlv a few hundred divers in Britain, and they are a very select bodv of men, with their own trade union. Most of them are Navy-trained men who begin their profession at about the age of eighteen. Contrary to general belief, the diver’s “life” is quite a long one. If a man retains his health and looks after himself, there is no reason why he should not go on diving in shallow waters, up till six-tv. Usually, however, no diver over the age of forty-five descends below a depth of 60ft. As for physical qualifications, the would-be diver must have a thorough-

ly sound heart, no pulmonary weakness, and, above all, must never have suffered from ear trouble, for it is upon the drums of the ear that the pressure when submerged beneath the water tells first.

Fat meg. do not make such good divers as lean men. They are more quickly affected by the peculiar exertions of the profession. The deeper the diver has to go the thinner he should be. The limit for a fairly fat man is about twelve fathoms; and beyond twenty fathoms it is vital to employ a thin man. Two hundred and seventv-five feet is the greatest depth at which divers in the flexible suit have worked. At this depth men have been able to stay up to 27 minutes. At such a depth, of course, there is no light except that supplied by the diver’s own lamps.

Sometimes a 2000 candle-power lamp is let down into the sea from above on the end of a chain. The diver may also work with the aid of portable submarine electric lamps. Perhaps his lamp will be fitted into his breast-plate,' from which it shines like a huge Cvelopean eye. Or he may use a hand lamp as well. The blackness of his surroundings depends entirely on the condition of the water. Visibility at comparatively minor depths is bad round English coasts. In the Mediterranean it is very good. The water is clear and the bright blue sky overhead also makes "a great difference in the visibility.

The only strange feeling the diver has, apart from being in a world of darkness and utter silence, is that he cannot move quickly. Each step he takes, every movement he makes with his arms, is slow and ponderous, just as though he were pushing his way through treacle. Probablv the most dangerous task a diver can be called on to undertake is not connected with the deep sea at all, but with the land. The exploration of a flooded mine gives him his most perilous job.

Here he has to descend into water thick with coal dust, where no lamps arc of anv use. He must proceed in pitch darkness, crawling cumbrous1v through narrow workings on hands and knees, with the possibility of a fall of coal occurring at anv moment. He is in tortuous, unfamiliar surroundings among which he mav easily lose his wav, for his only gjtide is his recollection of the diagram of the nit workings he studied before he descended. Some vears ago divers were requisitioned from the Siebe Gorman firm to explore a flooded pit in Scotland, where there had been a disastrous explosion. In parts of the nit they found the water was not deep enough to cover them. Sometimes it reached onlv to their knees.

The result was the operations were retarded bv their having to drag about with them the great weight of their diving dress, which, of course, is not noticeable when the diver is fully submerged.