Compressed Air Work And Diving 1909

ADJUSTMENT OF THE ESCAPE VALVE. 25 air is then temporarily checked, and the air will accumu- late in the back of the helmet and penetrate into the legs. If this happens the diver will be brought feet uppermost to the surface. This, of course, is highly dangerous, not only on account of the sudden decompression, if from any clepth, but because of the great risk the diver runs of getting caught in something or of striking his head against the keel of a boat. As the diver comes up, the air in his dress will expand, so that all the time his velocity will be increasing. The danger, therefore, of striking anything at the surface will be very great. To obviate, or at any rate minimise, this danger, a new type of dress, with tightly lacing up legs, has been introducecl into use in the Royal Navy. This prevents the air from getting into the legs, so that the cliver, should he fali clown, runs no risk from the air accumulating, but is immediately able to right himself. If a cliver for any reason wishes to blow himself up purposely, he will come to the surface in a perpenclicular position. We are assuming that the cliver is making his first descent on a laclcler reaching to the bottom and tightly lashed, say, to a pile. The professional cliver, in open water, will usually prefer a rope held to the bottom by a weight. The next thing for the cliver to do will be to see if he can inflate his Eustachian tubes. If he cannot do so, he wi 11 feel, when he has clescencled a few feet, a pain in the ears. He should then try swallowing, or moving his jaw about. If this does not relieve him, he should come up a few feet. When the nose can be held, as in an air- lock, it is quite easy, by biowing, to inflate the Eustachian tubes. This cannot be done of course in a helmet, but some divers find it helpful to press the nose against the face-plate and then blow,