Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

PROCEDURE OF THE DIVER ON THE BOTTOM. Going Down.—While standing- on the ladder, and before the front glass is screwed in, the diver should note the position of the shot rope, so that he may waste no time in getting to it after leaving- the ladder. He should also ascertain that his outlet valve is open and the tap (the excess air cock, or “spit-cock ”) closed. I he pump should be started before the front glass is screwed in. On hearing the attendant tap the top of the helmet, the diver may go on down the ladder till the water is up to his face. He then lets go the ladder, and allows the attendant to draw him to the shot rope by means of the breast rope (signal line) and air pipe. The diver grips the shot rope between his legs, holding on to it with his left hand while he adjusts his outlet valve with the right, his head being- just under water. During this brief pause he notes, from the sound in the helmet, that the pumps are working satisfactorily, and makes sure that no water i s coming in at the cuffs or any other part of his dress. \\ hen he is satisfied that all is correct, he waves his hand above the sur- face to show that he is ready. As soon as this signal is answered, he may go on down the shot rope hand over hand, keeping it between his legs and ready to check his descent at any moment. Pains in the Ears.—By the time the diver is a fathom or two down, he may probably notice pain in his ears, which may become worse as he goes deeper. This is due to the increasing- pressure of the air in the helmet on the outside of the ear drum. Ihere is a narrow passage (called the Eustachian tube) at the back of the throat through which air can pass to the inner side of the ear drum. If the Eustachian tubes were always freely open there would be as much pressure inside as outside the ear drums, and consequently no strain on them and no pain ; but in most persons the Eustachian tubes do not allow the air to pass through them very readily, and the pres- sure, therefore, is not balanced. Io get rid of the pain these passages must be opened. There are three ways in which a diver can try to accomplish this:—-(i) By swallowing several times; (2) By blocking up the nose as much as possible by pressing it against the f ront of the helmet, closing the mouth, and then making a strong effort at expiration so as to produce temporarily an extra pressure inside the throat, and so blow open the tubes ; (3) By yawning or going through the motions of yawning. So far as pain in the ears is concerned, a diver who is “fit” should have no difficulty in going down as fast as 10 fathoms a minute. Going Down loo Last for the Air Supply.—There is, however, a second obstacle in the way of going down very fast. As a man descends, the air which is loose in his dress over the chest becomes compressed into a smaller space as the pres- *o