410 Air-tight Subdivisions in Ships 



with it, if it is of a really extensive character; but, on the 

 other hand, the more easy is it (given the time) to get at it, 

 and deal with it from the outside. In all cases where the ship 

 has been damaged by touching the ground, or by torpedo 

 explosion under the bottom, and not involving the destruction 

 of the ship, the pneumatic method affords the readiest means 

 of combating the results. 



It must be remembered that a ship's hold when filled with 

 compressed air will be habitable ; that is, if an air-lock is provided, 

 men can descend into it and repair the damage, just as they 

 can descend into a caisson and dig out the foundations for the 

 pier of a bridge. 



The pneumatic method is, however, not only adapted for 

 keeping damaged vessels afloat, it is also useful for raising 

 sunken or stranded ships. For this purpose the salvage steamer 

 must be provided with air-forcing pumps as well as the suction 

 pumps which she usually carries. Having closed, and if 

 necessary strengthened the deck, by means of divers if below 

 water, she then pumps air into the holds of the ship, and at 

 once restores a large proportion of her original buoyancy to 

 her. If she does not rise, the other methods of salvage can 

 be applied in addition, and with much increased chance of 

 success. 



The principle of this method is not new. A very old device 

 in endeavouring to float, or to keep afloat, ships, is to fill as 

 much of their damaged hold as possible with empty casks. 

 A later modification of this method is to use inflatable 

 india-rubber bags. It may be remembered that after the 

 "Vanguard" sank Admiral Popoff, of the Russian Navy, sent 

 a large apparatus of this kind in order to render assistance in 

 trying to float her. Both these appliances are cumbersome. 

 A ship's hold is seldom quite empty when she sinks, and even if it 

 were, it is not easy to fill it under water with casks full of air, 

 or even with inflatable air bags ; and in any case it is difficult 

 in this way to fill more than a fraction of the hold with air. 

 The simple and efficient way of dealing with the matter is to 

 treat the ship's hold itself as the vessel to be filled with air. 



Compressed air is every day occupying a wider field as a 



