Air-tight Subdivisions in Ships 409 



for testing the efficiency of the bulkheads without the disagree- 

 able process of filling the compartment with water. It would 

 be only necessary to close the legitimate openings and get the 

 air in it up to a pressure equal to that of the ship's draught of 



r, and the result would be unequivocal. It is proper to 

 observe that the construction of an air-tight bulkhead would 

 differ slightly from that of a water-tight bulkhead, inasmu< 

 it will be exposed to the maximum pressure over its whole 

 surface, whereas the water-tight bulkhead is exposed to a 

 graduated pressure, being greatest at the keelson, and least 

 under the deck. 



irther advantage of fitting a ship with air-tight sub- 

 divisions is, that it not only gives her greater security against 

 foundering, but it affords a means of largely insuring her against 

 ri-ks of fire. This has more especial reference to merchant 

 ships. If the contents of a ship's hold catch fire, the easiest 



of putting it out is to stop the supply of air, and this can 

 be done if the hold i> air -ti.^ht. 



So far the damage to the ship is supposed to be a rent in 

 the bottom. If it is not in the bottom, but somewhere above 

 it, then the air can only expel the water down to the level of 

 the breach, whm tin- air will begin to escape tlu>u-li its upper- 

 most part. It will now depend on the supply of forced air 

 lable, how large a hole can be kept continuously filled by a 

 stream hing out. The area so occupi< -d U nece^.mlv 



closed to tin in trance of water, and if the machinery can >uppl\ 

 air at a sufficient rate, tin- whdr i nt < ,.n \>c tilled :ent 



of air. which, so long u> it i- k.-pt up, is as efficient a leak stopper 

 as a plate Ol -uld \><\ and meantimr tin- bottom of tin- 



held can be cleared by the ordinary bilge pumps. 



Rents in a ship are produced \vl 



run down, CM 1 by another, arc uMiallv M xtmsive and 



sen- mile--, tin- protected by an inner skin, 



inin any 



measures for res* P.ut \\itli an i: :uage 



be so far reduced as to t possible to deal \\ith it 



as above indicated. The higher up on the ship's side i^ 

 damage th- ten -uitai.l.- i, tin- pneumatic method for dealing 



