Safely at Sea Iron Vessels that will not Sink. 



ship's bottom and sides was divided Into a number ot 

 small water-tight compartments or cells, any one, or 

 lilmost ;inv number of which, could lie filled with water 

 without emlangei ing the slap's ability lo Hunt. Two 



thicknesses of iron bad u> be pierced before vital dam- 

 age could lie doiio to tlic vessel. This is called the 

 " cellular eonslrnclio'i," iii.d ships built in this way are 

 said to have a "double bottom" or a " double skin." 

 <;I.M:R.\L Al'l'LIl-AHlLlTY OF TI1K DOUDLE .SKI'S. 



Though be-t applied to vessels with tlio longi- 

 tudinal system of Irani in?, the cellular or douolo 

 noli 0111 can bo used iu ships having trans- 

 verse frames. This construction was used for 

 vessels of war, where great strength aud security 

 were ret|tiired, but by Johii Scott Russell it was 

 Introduced iu the Great Eastern, the first ineret.nnt 

 steamer having a double skin. It probably saved the 

 Croat ship in a moment of peril. 



The cellular system must uot be confounded with the 

 water tii' lit compartments or bulkneads used iu 

 all our transatlantic steamers. These bulkheads are 

 iron divisions running directly across the ship from side 

 to side, and from kelson to decks, dividing the vessel 

 into as many separate transverse compartments or di- 

 visions, any of which may by some accident become full 

 of water without endangering the safety of the vessel. 

 The construction of tiie bulkheads may be illustrated 

 by a long hall or room divided by walls into a number of 

 sections, communicating by doors. Shut these doors, 

 aud any of the divisions might be filled with, say smoke, 

 without the others beiug penetrated. Their distance 

 apart should be about equal to the ship's beam. The 

 idea originated with the Chinese in their trading vessels, 

 and was introduced iu England by Mr. Williams about 

 1839, or a few years earlier, in very nearly the present 

 form. 



The recent loss of so many iron vessels has given a 

 foundation to the idea that tneir strength is inferior to 

 that of the old wooden steamers, or at least that they 

 are more liable to sudden aud serious disasters, aud that 

 less rough usage will unfit them as efficient sea-boats. 

 What safeguards are provided against accident in our 

 ordinary transatlantic steamers 1 They are all provided 

 with water-tight bulkheads, which divide them into 

 seven or eight sections, and which are supposed to be 

 a sufficient safeguard against any ordinary calamity, 

 out they are not built on the cellular system, with 

 double skins from the keel to the water line. 



SAFETY OF CELLULAR CONSTRUCTION. 

 By this latter mode ot construction we actually reduce 



the chances of accident to a fraction, lor we place one 

 sLip inside the other, aud we make it necessary that 

 noth the inner and outer skin be pierced before we have 

 recourse to our water-tight bulkheads, which under all 

 iircuinstances are the last resort. The facts of the case 

 are these ; Our iron vessels, as at present built, are not 

 is strong as the old wooden ones. Less force is re- 

 quired to pierce a hole, either by a rock or by a collision, 

 through the plating of our iron steamers than was re- 

 quired to break through the seven or eight inches of 

 solid wood used in the vessels of a fsw years ago. 



Though the desire of the owners of steamships to make 

 money has thus induced them to depart from the sound 

 practice by building single-skinned ships weaker than 

 their modern predecessors, it is no argument against 

 the use of iron m the construction of vessels. The more 

 we study the science of shipbuilding the more we learn 

 ;o appreciate the fact that a vessel is to bo regarded 

 (imply as a beam or girder, subject to different strains, 

 lepeudiug upon the way she happeua to Uo sup- 



ported by tbewave>, win-tiler ill the ml. ).,!, li 

 wave, or Whether by two w a . . -.,,,.,, :, I . ., -|, , ,,,'. T. 

 iu calculations, we treat a sliip, ;md as tin- iv-ult of our 

 figures we lind :b ;1 t the stiengih mil I hi- pl:ir | in i he 



bottom and iu the top of our vessel; that tin- resisting 



power of the upMci- deck lo crii-hnr,' an I tensile .-train , 



must be about equal to that or the Nim.'.s hot; ..m. n 



\\ill be observed in looking ut an Iron lieam or gir ler 

 that the strength is placed at th.< top an. | bottom. In 

 this case the dictates of both science and pr.u t 06 have 

 been observed. Jiut, in opposition to this BJ ' m, which 

 has been proved to be correct, our pr - ,t iron \,-^eis 

 grow gradually weaker from the bo t m up till tin- 

 upper deck is the weakest of i.ll. Now hi n-n.-i b c..ald 

 be insured in the bottom, which shoulil at leusl 'nnal, if 

 uot more than equal, that of our wooden ships; but to 

 do this would require that the iron bo mn>-h thicker 

 than at present, aud the weight would bo increased in a 

 greater proportion than the strength. 

 STRENGTH INCREASED IX PROPORTION T't \V1 K.III. 



Here comes iu the value of the cellular construction 



with the double bottom ; the weight is incr<-a^efi m pro- 

 portion to the strength, and wo obtain a result wliicii 

 for safety is far ahead of that secured by the mas-t of 

 wood In the wooden ships. If the longitudinal system 

 of framing is adopted, we shall also have a gain as to 

 weight over the transverse system, and this amount of 

 iron saved can be used in making the upper deck cel- 

 lular also, as was done in the Great Eastern, thus 



making our vessel conform closely to the structure of 

 a girder or beam, the result which we wisii to onrain. 



List us see whether the cellular svstem has d> m> any- 

 thing to prevent vessels sinking. When the Great K i-t- 

 ern was entering the Sound she struck on a rock and 

 perforated her outer plating. The d mi ige \v s serious ; 

 seven holts were made, one 85 feet long by four or five 

 wide. Transverse bulkheads as put into a ship would 

 not have saved her; she would have sunn so rapidiv 

 that her passeuirets could not have re/iehed the upper 

 deck, had she not had a double bottom three feet in-nlo 

 of the one pierced, which being intact kept her afloat 

 and would have continued to do so had she desired to 

 make the voyage home again. She was repaired in New- 

 York without beiug removed from the "water by Mr. B. 

 S. Renwick. Other cases can be given of naval vessels 

 with the cellular construction which have been saved 

 after almost equally severe damage to their outer 

 plating. 



Two diagrams will more cloarlv explain thr constiyic- 

 tion of vessels built with the longitudinal system of fr itn- 

 ng, and with double bottoms. No. 1 Nh-_ us a cross section 

 of such a ship, and No. 2 is an enlarged view ol tin- bottom 

 from the ki-el to the water lino. Tin- parts lettered .V 

 B, C, D, are the longitudinal frames running the length 

 of the ship, the parts marked d an- the plalo of the 

 Inner skin meeting tbe outer plating at the water line, 



on a point a little above it. The gusset piece" art- 

 worked in to strengthen the construction, the ribs of 

 angle iron, as shown by d. also giving still HSS to tin- sides 

 and serving as braciufa's to tho longitudinals A, JLJ, C, D. 



