50 



NA TURE 



\_Nov. 15, 1883 



diagrnms" or "curves of stability." These gentlemen 

 feared that to the average ship-captain such curves and 

 diagrams would be unintelligible, and therefore of no 

 jwactical value. It must be admitted that there is some 

 force in this contention ; but on the other hand it is 

 obvious that a very moderate amount of instruction ought 

 to suffice to make information of the kind intelligible and 

 useful to an educated seaman. 



It may be worth while to mention what is the established 

 practice in the Royal Navy in this matter. Each of Her 

 Majesty's ships is provided with a "Statement of Stability," 

 in which appears a record of the " metacentric heights," 

 corresponding respectively to the " fully laden " and the 

 " extreme light" conditions of the vessel. There is also 

 a record of the calculations of stability at various angles 

 of heel ; the angle at which the stability attains its maxi- 

 mum and that at which it vanishes being noted. In cases 

 where special precautions are needed special standing 

 orders arc given. For instance, in some low freeboard 

 ships it is stringently ordered that a certain maximum 

 load draught shall not be exceeded, because any diminu- 

 tion of the corresponding freeboard would cause an ob- 

 jectionable decrease in the range and area of the curve of 

 stability. Again, in some vessels, as coals and stores are 

 consumed, the stability is considerably diminished, and 

 then orders are given that the ship shall not be lightened 

 beyond a certain miniinum draught, that draught being 

 maintained if necessary by the admission of water-ballast. 

 All these regulations are based upon careful experiment 

 and detailed calculations. In the original design of the 

 ships close attention is bestowed upon the question of 

 their sufficient stability ; and when the vessels are com- 

 pleted, an experimental check is put upon the intentions 

 of the design, any necessary corrections being made in 

 the original calculations. But it is right to remark that 

 war ships are much more easily dealt with than merchant 

 ships, because definite positions are assigned in them by 

 the designer for all the weights carried — whether they be 

 armour, or guns, or coals, or ammunition, or outfit. 

 Hence it is possible to state distinctly what is the sta- 

 bility in the fully laden condition, and what are the ex- 

 tremes of possible variations in stability as coals, stores, 

 &c., are consumed. In merchant ships, as was remarked 

 above, the designer and builder have no corresponding 

 control over stowage, and in practice very considerable 

 variations in stowage necessarily occur. Leaving this 

 difference aside for an instant, it may be stated that in 

 the Royal Navy the information given on " Statements of 

 Stability " is highly valued and well understood by naval 

 officers. This result is, no doubt, attributable in a large 

 degree to the fact that at the Royal Naval College for 

 many years past classes have been arranged wherein 

 naval officers receive instruction in the elements of naval 

 architecture, and especially in the methods of interpreting 

 the various statements and drawings issued by the 

 Admiralty to the ships of the fleet. Similar instruction 

 could not fail to be of service to officers ot the mercantile 

 marine, and t"e Admiralty have made provision in the 

 Regulations for the admission of a certain number of such 

 officers annually ; but as yet no advantage ha^ been taken 

 of the permission. Either in this way or in sume other, 

 instruction must be obtained by merchant captains if they 

 are to exercise an intelligent control over the loading of 



their vessels, and to insure the provision of sufficient 

 stability. 



It seems very probable that one result of recent occur- 

 rences and discussions will be the grant of greater freedom 

 to shipbuilders in choosing the dimensions for new ships 

 than has been customary hitherto. And it may be anti- 

 cipated that increasing attention will be bestowed upon 

 investigations of stability in connection with new designs. 

 But whatever improvements may be made in the general 

 practice of shipbuilders, the responsibility for manage- 

 ment and loading must always remain with the owners 

 and commanding officers of merchant ships. Ill-advised 

 action on their part might render futile all the precautions 

 of the designer. He may have secured what seenrs a 

 good margin of stability, on the basis of some hypothetical 

 arrangement of a certain dead weight which was supposed 

 to be the maximum a ship would carry ; and yet in 

 practice some more critical condition of loading may 

 arise which must be dealt with by those in charge of the 

 vessel. 



Having regard to the very considerable variations in 

 the character of the cargoes carried by the great majority 

 of merchant ships on their several voyages, it appears to 

 be highly important that owners and captains should 

 have placed in their possession full information respect- 

 ing the stability of their ships ; and that they should be 

 able to make intelligent use of this information. One of 

 the most valuable pieces of information which a captain 

 could obtain for a laden ship would be her " metacentric 

 height," and there seems no reason why an intelligent 

 officer who had been furnished with a "metacentric 

 diagram," and understood its use, should not experi- 

 mentally determine for himself before leaving port what 

 measure of " stiffness" his ship possessed, and at what 

 vertical position the centre of gravity was placed (if the 

 conditions of loading were of an unusual character). 

 He would then have a more certain assurance of the 

 sufficiency or otherwise of the stability of the ship than 

 he could otherwise possess ; and this assurance might 

 easily be made to extend not merely to the initial stability 

 but to the stability at large angles of inclination. It may 

 be urged that it is too much to hope for any such experi- 

 ments, or for such an advance in knowledge ; and that in 

 the stress of business time cannot be found for such 

 elaborate inquiries. Possibly one may be too sanguine 

 to indulge this hope ; but inclining experiments of the 

 kind indicated are neither lengthy nor costly operations, 

 and their value as indications of the probable safety or 

 danger of laden ships cannot well be over-estimated. 



The necessity for carefully considering the stability of 

 merchant ships is not a matter of dispute. All concerned 

 may be assumed to desire some practical solution of the 

 problems involved in securing sufficient stability. And 

 on a review of the whole subject it will probably be ad- 

 mitted that all three classes interested — the shipowner, 

 shipbuilder, and ship-captain — must accept their several 

 responsibilities while working towards a common end. 

 The shipowner may be presumed to know best the special 

 requirements to be fulfilled in any new design. It is the 

 duty of the designer to make sure that appropriate 

 dimensions and proportions are secured in association 

 wi'h the fulfilment of these requirements, or to point out 

 the impossibilty of such an association. And, finally. 



