250 SOCIETY NAVAL ARCHITECTS AND MARINE ENGINEERS. 



(2) The portion forward of the machinery space ; and 



(3) The portion abaft the machinery space. 



For steam vessels the permeability of the machinery space, including the double bot- 

 tom in wake thereof, shall be taken as 80 per cent. For vessels fitted with internal com- 

 bustion engines the corresponding permeability shall be taken as 85 per cent, unless it is 

 proved by actual calculation that a lower figure may be adopted, provided that in no case 

 shall that figure be less than 80 per cent. 



The permeabilities for spaces forward and aft of the machinery space shall be as fol- 

 lows: 



(a) Sixty per cent in cargo spaces, bimkers (permanent or reserve), storerooms, bag- 

 gage and mail rooms, chain lockers, watertight shaft or pipe tunnels, and fresh-water tanks 

 above the double bottom. 



It must be proved that the spaces just enumerated are practicable for the purpose in- 

 tended and that they are in fact to be so used. The same permeability shall not be as- 

 signed to any other space without the approval of the Administration. 



(&) Ninety-five per cent in passenger and crew spaces, peaks, trimming tanks exclu- 

 sively so used, double bottoms, and all other spaces not specifically appropriated to one of 

 the purposes indicated in the foregoing section (c). 



If in a 'tween deck space inclosed by complete transverse permanent steel bulkheads 

 any portion thereof is appropriated to passengers, the whole of that space shall be regarded 

 as passenger space; and, similarly, 'tween deck spaces appropriated for the carriage of 

 either passengers or cargo shall be regarded as passenger spaces. 



Where the spaces before or abaft the machinery space below the margin line consist 

 partly of spaces mentioned in section (a) and partly of spaces mentioned in section (b), 

 the average percentage of permeability shall be determined separately for each end by the 

 formula 95 — 35 r, where r is the ratio between the volume of the spaces mentioned in sec- 

 tion (a) and the total volume of the space in the portion of the ship under consideration. 



Article VIII. 



PERMISSIBLE LENGTH OF COMPARTMENTS. 



(1) The maximum permissible length of one compartment having its center at any 

 point in the vessel's length is obtained from the floodable length (Article VI) by multiply- 

 ing that length by an appropriate factor, called the factor of subdivision. 



(2) This factor of subdivision depends on the length of the vessel, and, for a given 

 length, varies according to the nature of the service for which the vessel is intended. This 

 factor decreases in a regular and continuous manner — ■ 



(a) As the length of the vessel increases; and 



(b) As, for a given length, the vessel departs from the type of vessel engaged in a 

 mixed cargo and passenger service, and approaches to the type of vessel primarily engaged 

 in the transportation of passengers. 



(3) For each of the two types of vessels referred to in the previous paragraph (2) 

 (6) the variation of the factor of subdivision may be expressed by a curve, of which the 

 coordinates represent the length of the vessel and the value of the factor. The following 

 table gives certain points on two curves the higher of which corresponds to the minimum 

 requirements for the "mixed" type, and the lower to the minimum requirements for the 

 "passenger" type. 



