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

sure increases, and unless the ptimp is delivering air fast enough to make this loss good, the air in the dress will disappear, while that in the helmet may be at a lower pressure than the surrounding water, the result of this state of affairs being that the diver gets a very severe squeeze. To avoid this the diver must keep his valve nearly closed, and go down at such a rate that there is always a little air over his chest, and a small amount escaping from the valve in the usual way ; the faster the pump is going the quicker the diver can get down. In practice it has been found easy to get down to 30 fathoms in a minute and a half with two Siebe - Gorman two - cylinder, double-acting pumps heaving for one diver. Provided there is enough air in the dress, as explained above, and the ears are not very painful, a diver may confidently slide down the rope at a good speed. Diver to go Down Fast.—To hang- about on the shot rope when going down wastes time, and by increasing" the time under water adds to the danger on coming up. If, on the other hand, severe pain is felt in the ears, and the remedies suggested will not act, there is nothing for it but to wait on the rope for a minute or two, when the pain will get less and less, and enable the diver to g’o down a few more fathoms till it stops him again. On reaching the bottom the diver will signal the fact by one pull on the breast rope, which the attendant answers in the usual way. The diver should now see that the shot is just touching the bottom ; if necessary, signalling for it to be lowered or pulled up. (If the shot is off the ground, the breast rope or pipe may get dipped under it, which is undesirable.) He then clears away the distance line, coiling it in the left hand ; the left wrist may be slipped through the loop at the end as a precaution against dropping the line in a moment of forgetfulness, for without the distance line it will generally be impossible to find the shot rope again. The diver should now get to his work without further delay. Management of the Outlet Valve.—-Comfort under water depends largely upon the correct adjustment of the air regulating outlet valve. This valve is correctly adjusted when there is enough air under the corselet to support the weights so that the diver does not feel any sense of heaviness about his shoulders, and yet is heavy enough to stand firmly on the bottom. When sitting or standing up under water, the valve can be easily screwed up until these conditions are satisfied ; the surplus air will then escape freely, no further adjustment being- required. One-half or three-quarters of a turn open will generally be found to be about right But since divers on the bottom are very often in a crawling or lying position, the state of affairs is then different. The air always fills up the highest part of the dress (when lying face downwards, the back) before it can escape from the valve, which is at a lower level, however widely the latter is opened. Whenever a diver is keeping his head low, air may accumulate in this way, float him up from the bottom, and so blow him to the surface. The remedy is to empty the air out of the loose parts of the dress at frequent intervals.