April lo, 1884] 



NA TUKE 



561 



ceivalile circunutances of loading. The due preservation of 

 stability in such cases requires to be watched and provided for 

 by those who control the loading. 



It is erroneous to suppose, as appears to be sometimes done, 

 that a cargo-carrying steamer should be so constructed and pro- 

 portioned as to run no risk of becoming unstable, however she 

 may be laden. If this idea were acted upon, such a mode of 

 preventing instability, however easy and plausible it may at first 

 sight appear to be, would only defeat the desired object of pro- 

 moting safety at sea, because it would make many vessels dan- 

 gerously still" when laden with some classes of cargo. The true 

 and reasonable mode of procedure is not to attempt to construct 

 a ship so that she will be stable however she may be laden, but 

 to see that any tendency she may have towards instability — if 

 any such exist — is understood by those in charge of her, and 

 that she is always laden with careful reference to it. There are 

 no steamers afloat, whatever tendency they may have towards 

 instability as sometimes laden, that they may not be kept per- 

 fectly safe if treated with full knowledge of what their stabUity 

 is, and the stowage regulated accordingly. One great problem 

 that the mercantile naval architect has just now to solve is, how 

 any dangerous features of a ship's stability are to be made clearly 

 known to those in charge of her, and in what manner they can 

 be best taught to regulate the loading in cases where special care 

 may be required. 



It is sometimes supposed that owners and masters are not only 

 negligent, but indifferent in this matter ; and that they deliberately 

 refrain from any consideration of it. It has been stated that 

 there are no owners who avail themselves of the knowledge of 

 stability now readily obtainable as a guide in the stowage and 

 safe working of their ships. These are views which my experi- 

 ence does not enable me to indorse. I have found, on the 

 contrary, that many of our leading owners of passenger and 

 cargo steamers are extremely anxious about the matter ; and not 

 only anxious, but they adopt all means that lie within their 

 power of dealing practically with it. The great stumbling-block 

 they usually meet with, however, is the intrinsic difficulty of the 

 subject. 



Owners and masters have their own modes of thought and 

 their own practical methods of ascertaining and regulating the 

 stability of their ships, which are often quite sufficient for the 

 purpose. They can very well comprehend whether a vessel will 

 stand up when light without ballast, and, if not, how much it 

 will require to make her do so. Tlieycan also understand if she 

 is too stiff when laden with heavy dead-weight cargoes placed 

 low down in the hold : or if she becomes unduly tender when 

 laden with light cargoes of which more than a certain quantity is 

 placed in the 'tween decks. They have not, however, had the 

 technical training and experience which is requisite to enable 

 them to understand and deal with metacentres, centres of gravity, 

 and curves of stability ; and to make all those allowances for 

 constant variations in draught of water and position of centre of 

 gravity which the different cargoes they carry render necessary. 

 Some owners have recently obtained curves of metacentres and 

 curves of stability for their ships, constructed for certain draughts 

 of water and descriptions of cargo. These curves, as a rule, 

 are put to no real practical use by them, as they find themselves 

 unable to apply stability information in this highly specialised 

 form to the accurate and reliable treatment of the various ques- 

 tions that arise in loading, or to compare it with the results of 

 their own judgment and experience. 



The above course has lately been taken in many cases because 

 of the opinions which ha\'e been expressed that the way to pre- 

 vent ships being lost through want of stability is to supply the 

 masters with particulars of the metacentric height and a curve or 

 curves of stability. The Wreck Commissioner advocates this 

 course, and appeals to entertain no doubt as to its desirability 

 and practical efficacy. His object is a most praiseworthy one, 

 but I do not believe it to be possible to carry it out in the way 

 he suggests. The advice he gives is based upon the belief that 

 shipmasters and others who have to do with the loading of ships 

 can readily be made to understand what curves of stability repre- 

 sent, and to use them correctly in practice. I have during the 

 last two or three years frequently tried to carry out this view, but 

 have never yet met with a shipmaster — and I have had to do 

 with some of the most capable and intelligent of the class — who 

 could l)e got to understand curves of stability sufficiently well to 

 be trusted to work with them in practice, or who would even 

 l)rofess that he could do so. 



If mercantile steamers could always be loaded in a uniform 

 manner, it might be possible to represent their stability in all 



conditions with sufficient accuracy and completeness for all 

 working requirements by means of a curve or curves ; but as 

 regards tlie vast bulk of merchant shipping there are no curves 

 of stability which could possibly be constructed, except that for 

 the absolutely light condition, which would be likely to represent 

 the actual stability of the ship except on a very few occasions 

 during the whole of her career. The only use to which any 

 curves of stability that might be furnished could, as a rule, be 

 put is to furnish data for enabling the stability under different 

 conditions from those for which they were constructed to be 

 estimated. This is an operation which masters of ships cannot 

 perform, and which would only be likely to confuse and mislead 

 them if they were to attempt it. 



The Wreck Commissioner laid great stress upon the use it 

 would have been to the captain of the Amtral at the time of the 

 accident if he had been in possession of curves of stability and 

 calculations which had been constructed for that condition, and 

 laid before the Court. It does not appear to have been seen that, 

 whatever particulars of calculations and curves of stability had 

 been supplied to the captain, he could not by any possibility have 

 had those which related to the condition of the ship at or some- 

 what prior to the time in question. Her stability on that occa- 

 sion was determined by the amount of weight she happened to 

 have in her, and the position of its centre of gravity ; and this 

 was the result of a chance state of things which only existed at 

 that precise moment, and which may hardly occur again during 

 the existence of the ship. If we assume that this information 

 would have taught the captain more about her stiffness than he 

 already knew through his previous experience of the vessel, still 

 it could not have been supplied to him beforehand by any one. 

 All that could have been done was to supply him with particu- 

 lars of the stability at other draughts and with other positions of 

 the centre of gravity, leaving it to him to estimate from these 

 what it would be at the time in question if he thought it desirable 

 to do so. 



I need hardly say again that the operation of constructing 

 curves of stability for a particular draught of water, and position 

 of centre of gravity from the results of calculations made in the 

 usual way for certain other draughts of water and positions of 

 centre of gravity, is an operation wliich requires a well-trained 

 naval architect to perform. No one knowing the subject can 

 suppose that masters of vessels have had either the training or 

 the experience to qualify them for performing such an operation, 

 or can help fearing that the result of their attempting it might 

 be misleading. As I have already said, I have never been able 

 to discover a shipmaster who could be safely trusted to do it, or 

 who cared for it to be supposed that he could. It is hopeless, 

 at present, to expect either shipowners or shipmasters to use 

 metacentric heights and curves of stability as a practical guide in 

 stowage ; and it is necessary to put stability information before 

 them in a simpler form, and one which fits in better with their 

 own ideas and modes of procedure, if it is to be utilised in fur- 

 nishing any real guide towards safety in loading. It is qitite 

 unnecessary for us to require such persons to become specialists 

 in the science of naval architecture before applying the results of 

 scientific calculations to safeguarding the stability of their ships. 

 I have myself been obliged to give up all attempts to deal satis- 

 factorily with the question by supplying curves of stability and 

 other information of that class. 



The method which I have adopted is the following, and I 

 now lay it before the Institution, chiefly for the purpose of 

 eliciting opinions upon the subject, and as a suggestion to others 

 who may be working in the same direction and have experienced 

 similar difficulties with myself. In advising upon how a steamer 

 should be treated and loaded so as to be kept safe in respect of 

 stability, I state (i) the quantity of ballast, if any, that is re- 

 quired to enable her to stand up when quite empty, without 

 water in boilers or tanks, coal in bunkers, and with a clean-swept 

 hold, and to be stiff enough for all working requirements in 

 dock or river ; (2) if she is to be employed in carrying homo- 

 geneous cargoes, what proportion of the space in the 'tween 

 decks it is safe to fill with such cargo, after the holds are full, 

 and what weight of ballast is required in the bottom to enable 

 the vessel to be loaded to her maximum draught with such cargo ; 

 (3) if required to carry two or more kinds of homogeneous cargo, 

 such as grain and cotton, grain and wool, grain, meat, and wool, 

 &c., the best mode of stowage, and whether or not the space in 

 the 'tween decks can be filled with the lightest of the cargoes, 

 and in what circumstances ballast, and how much of it, will be 

 required ; (4) if not intended for homogeneous cargoes, but for 

 general cargoes, or partly homogeneous and partly general, the 



