Compressed Air Work And Diving 1909

24 COMPRESSED AIR WORK. diving ladder, for fear he might stumble. When he is a few feet below water he should stop to adjust his escape valve. The proper adjustment of the valve is rather important. The valve is kept closecl by a weak spring. When the valve is screwed up the power of the spring is increased so that less air can escape. If the air pressure gets too high the air will penetrate into the dress, and then the diver will be brought rapidly to the surface, or “ blown up,” on account of the increased displacement of water, for with the valve properly adjusted the dress clings tightly to the body. If, on the other hanel, the valve is too mueh open, the pressure on the body will make breathing very clifficult. The most comfortable adjustment will be when the air in the dress is just sufficient to take the load of the heavy lead weights off the diver’s shoulclers. A very interesting experiment was made by Dr Haldane upon himself, during his investigations on behalf of the Admiralty Committee, to show the effeet of varying the pressure in the diving dress. The apparatus Lised by Dr Haldane was the orelinary dress and helmet, but in place of the ordinary escape valve, a rubber tube was fitted, about two feet long, with an orelinary valve at the end of it. During the experiment this valve was kept fully open, and Dr Haldane found that with the valve held a few inches above the helmet the pressure on the chest and abdomen was so great that breathing was quite impossible. With the valve held at the top of the helmet breathing was possible, but extremely laboured ; at the ordinary level still laboured, especially during exertion or with a short air supply; and two or three inches lower was mueh easier (see “ Report,” page n). The clanger of biowing up accidentally is greatest when a cliver suddenly stoops clown. The outflow of