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

watches for the object while the boat is kept under way. In these cases special ar- rangements must be made so that the diver may stop the boat directly he sees the object, lest it should be lost again. One way is to keep the shot dragging on the bottom with a man attending the rope. On receiving one pull from the diver, the shot rope and the diver’s pipe and breast rope are paid out freely till the boat is stopped and brought back so as to plumb the shot, when her anchor may be carefully lowered to the bottom clear of the diver {not when he is on the grating). In very clear, shallow water the catoptric tube may be usefully employed. Work in a Tideway.— In places where work has to be carried on in a tideway, the responsible official in charge of the operations should make himself acquainted with the times and run of the tides, and the duration of slack water, and arrange to be on the spot in good time. The behaviour of the shot rope gives a good guide as to when a man may usefully be sent down. When a 50 lb. sinker refuses to remain on the bottom, but is swept off by the tide, it will generally be found impossible for a diver to do anything on the bottom. When working in great depths where a long time has to be spent on the shot rope in coming- up, the diver must be called off the bottom in good time to prevent him from being exposed to too strong- a tide while on the shot rope. On such occa- sions a sinker must be used of such weight as to render it impossible for the diver, while still on the shot rope, to be swept up to the surface by the tide. Diver accidentally blown up to be sent down immediately. The only treat- ment which is likely to be of any use to a man who has blown up from deep water is to send him down again at once, even though he has already begun to suffer from the effects of the sudden decompression. If he be helpless, his valve should be opened, and the man lowered down by his breast rope and pipe, another diver being- sent down to look after him as soon as possible. The official in charge must act promptly and without hesitation in such circum- stances, getting the diver under water again without losing a moment. After a few minutes at the depth from which he came, the diver can be brought up in accordance with the scale. Joining up 1 wo Pumps to One Diver for very deep Water.—To join up two or more pumps to one diver, the four-way junction described on page 30 is employed. The air delivery nozzle of each pump is connected to one of the arms on the nozzle by a 30, 45, or 50ft. length of air pipe. (In the case of the Siebe-Gorman two- cylinder, double-acting type of pump, as used in the British Navy, the pipe connecting the arm of the four-way junction must be joined up to the left hand air delivery nozzle of the pump.) 1 he diver’s pipe is joined up to that arm of the junction which has no tap. If only two pumps are connected up, the tap on the fourth arm is kept shut, the others being open. Before connecting the air pipe to the diver’s helmet, its end is blocked 45