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

surface of the water. Attempts have been made to remedy this defect by fitting the apparatus with cork life-belts, or with a chamber, or chambers, already inflated with air, but these are found to be impracticable, owing to the necessity of employing heavy weights to keep the wearer down, and also by reason of the dangerous velocity with which he would rise to the surface on the removal of the weights. To obviate these disadvantages a flexible air-chamber, as before described, is attached to the apparatus in such a way as to enable the wearer himself to inflate it when he reaches the surface, and thus render himself buoyant enough to float when the window of the helmet is open. One great point about the apparatus is that it can be exercised in. We would propose to let every “ submarine ” man, as part of his training, go under water in the helmet, toget used to it. Men equipped in the helmet should also be trained in the boats in finding their way out of the conning tower or torpedo hatch. As a matter of fact, the British Admiralty have gone further than this in having, at Portsmouth, a huge tank of water, at the bottom of which is erected a “ skeleton ” submarine boat. At the surface is fitted an arrangement for lowering and raising an air-lock, as shown in photos Nos. 42 and 43. The men, having- first been trained to put the dress on quickly (see photo No. 41), practise getting- into and out of the air-lock. They are afterwards lowered in the lock to the bottom of the tank, where they enter the “ submarine ” and find their way to a ladder leading up to the conning tower, the hatch of which they open. Then they either float to the surface or return to the starting point, the operations being repeated until the officer in charge considers the men proficient. For the purpose of taking a clear photo of No. 44, the water in the tank was lowered. Photo No. 36 shows a man who has just floated to the surface. It will be readily understood that this training air-lock, used as described, brings about practically the same conditions as would obtain in a submarine boat which had been flooded, the air in the former being compressed just as that in the air-lock of the submarine. There is one point that demands notice, and that is the effect of water pressure. It seems difficult to understand how it is possible for the men toget out of a submarine and not be at once crushed by the pressure of the water, but water pressure per se has no effect on the diver, provided that the pressure of the air in the dress is the same as that of the water outside. We have already explained what happens when a submarine is holed by accident. The water pouring in will, if the hole is at the top of the boat, gradually replace the whole of the air in the vessel ; but if the hole is below the highest point, then the water as it enters will compress the air until the pressure of the latter is equal to that of the water outside. If, now, the men in the boat close up their helmets whilst standing in this reserve of compressed air, the pressure of the air in the helmet will be the same as the water pressure, and the conditions of safety are secure. The crew can now, without difficulty, open the torpedo hatch, or the hatch of the conning tower, and ascend to the surface. 00 00