Air-tigJit Subdivisions in Ships 407 



The bottom of a ship at sea is very inaccessible. If she remains 

 fast on the rock it is usually impossible to get at the leak either 

 from the outside or from the inside. If she is afloat, and will 

 keep afloat long enough, the leak can often be efficiently dealt 

 with by passing a tarpaulin or sail under her bottom. But 

 this is by no means a simple or easy operation, even when 

 performed as a matter of drill with plenty of time, and in the 

 absence of excitement or danger. 



When a ship is sinking, she does so because water has got 

 into her either from above or below, and has displaced the air 

 with which she was charged. In order to stop her sinking and 

 to raise her to her original level, it is necessary to reverse the 

 operation and replace the water again by air. If the water 

 has come in from above, by shipping seas, this can be effected 



-action pumps, which throw it overboard again. If it has 

 entered and is entering through a hole in the bottom of the 

 vessel, it is necessary not only to remove the water whirh has 

 entered, but to stop any further entry, and this is achieved by 

 im -an- which enable us to thrust the water out again by 

 the same way as that by which it entered. 



If we consider a ship's hold, and assume that the deck 

 covering it above, and the bulkheads shutting it off fore and 

 aft, are all sufficiently strong and air-tight, tin -n if the whole 

 bottom were allowed to drop out, her stability being otherwise 

 assured, she would be very little the worse; the water would 

 rise in her hold only until it had so far compressed the an 

 that its tension exactly balanced the pressure of the column 



vater outside, ami matin- might -at. 1\ ivmam in tin- 

 conditin: iihiium alm<>-t imlrtinitrlv. Tims lv making 



thr main deck of a modern -hip. t<> \\hi.h tin- wal 

 bulkheads are carried up A mild be practically 



proof against all li-k t inkm- IP in damage to her bottom. 

 not think that thrrr would be any difficulty in making 

 the compartments of a ship pa ^ht or more prop* 



that the rise of tension <jm kl\ produced by 

 the entry of \\at-r tlm-ngh a * rJOfH 1< ak. would at once close 

 any joints or small < . 



lock giving to a submarine caisson is kept 



