422 



NATURE 



\_August 30, 1883 



must force extended calculations upon all those who here- 

 after undertake to launch ships upon the stability of which 

 any doubt can by possibility exist. 



It is pretty widely regarded as a remarkable fact that 

 there should have been any deficiency in the knowledge 

 of shipbuilders concerning the conditions or possible con- 

 ditions of the stability of ships at their launching draughts. 

 But to me this deficiency seems the most natural thing 

 possible. It needs no explanation to those who remem- 

 ber what immense transformations and extensions have 

 come upon the shipbuilding trade during even my own 

 professional experience. I well remember looking with 

 wondering interest in Sheerness dockyard at the first iron 

 ship ever seen there ; and yet the construction of iron 

 ships had become so universal fifteen years ago that I 



wrote my work on " Shipbuilding in Iron and Steel " to 

 meet a widespread necessity, the idea of writing descrip- 

 tions of wood ships having already passed away. I 

 equally well remember the building at Sheerness of the 

 first screw steamship ever constructed there ; but where 

 now are any but screw steamships built for ordinary 

 ocean work? Some sailing ships and some paddle 

 steamers doubtless are built even now ; but the screw 

 steamer has almost undisputed possession of the world's 

 ocean trade. With these changes have come in wholly 

 new developments of shipbuilding science, and the pre- 

 sent is not by any means the first instance in which it has 

 fallen to my lot to point out errors of doctrine — false de- 

 ductions from former practice — which were misleading 

 the shipbuilder. In the case of the strains to which ships 



• 5 or a foot 



FIG. 7. 



CURVE of STABILITY of S.S. 



H AMMONIA, as launched. 



30 ' 35 40 45 50 



ANGLES OF INCLINATION 



are subjected, the deductions made by the most eminent | 

 men who discussed the subject scientifically at the end i 

 of the last and the beginning of the present century 

 seemed to me to be irreconcilable with the conditions of 

 modern ships, and after lengthened investigations I found 

 that they were not only wrong, but in some cases the re- 

 verse of the truth, and I contributed to the Royal Society 

 a paper on the subject which has brought modern theory 

 and modern practice into better relationship. In the : 

 matter of stability it was most natural that as we aban- 

 doned the employment of wind as our propelling power — 

 which of course imposed upon ships the necessity for 

 large stability to withstand the wind-pressure — ship- 

 builders were able to resort to greater proportionate 

 length and to enlarged proportionate area of midship 

 section; and thus to bring about conditions in which 



large initial or early stability, so to speak, fell out of de- 

 mand. Nor is it easy to say when deficient stability 

 would have come under close investigation, had it not 

 been for the accident of certain ships of very low free- 

 board coming under consideration at the Admiralty, as 

 explained in my Report. These led to the calculation of 

 stability at successive angles of inclination, and to the 

 method of recording the results in the form of the " curve 

 of stability" previously described. But besides the 

 change of the seagoing ship, there has been the enor- 

 mous extension of its employment, our carrying trade on 

 the sea having increased by leaps and bounds. Every one 

 knows that when the demands of commerce are very 

 urgent, science and scientific research are apt to be 

 neglected. The necessity for great carrying uower and 

 speed at sea has been attended by an equal necessity for 



1 FOOT 



9 

 3 



7 



6 



5 



FIG. 8. 



CURVES of STABILITY of S.S. 

 DAPHNE'.' as launched. 



A. TO MAIN DECK. 



B- INCLUDING POOP. 



C. TO TOP OF BULWARKS. 



/ 



/ 



y 



quickening the loading and discharging of ships in port, 

 and consequently steam windlasses ind cranes, and many 

 other modern appliances involving upper weight have 

 come into vogue, and their effect upon stability has not 

 been always considered. From these and other causes 

 there has been brought about that somewhat extensive 

 employment of ships of small stability, or of no stability 

 at all in themselves, to which it lately became my duty to 

 direct attention. It is no doubt the general belief that a 

 high-sided ship having some initial stability, will, as she 

 inclines, gather large additional stability, and will retain 

 some even at very large angles ; that, as my Report states, 

 has greatly encouraged people to be satisfied with very 

 small initial stability, in some cases with none at all, and 

 even less than none. Many steamships of large tonnage 

 have been built of late years for influential steam com- 



j panies and other owner?, which ships " are totally in- 



I capable of floating upright without the aid of ballast or 



I of cargo, and which cannot be unloaded in dock without 



I being held upright with hawsers attached to the shore. 



Such ships, even when capable of floating unballasted 



without capsizing, can only do so by lolling over at large 



angles of inclination, and there finding a position of stable 



equilibrium. When carefully watched over and stowed 



with suitable cargoes, these ships can usually be made 



' safe at sea, and sometimes even safer than ships with 



larger initial stability but less range— a circumstance to 



which undue prominence has perhaps been given, and 



which has diverted many from the grave elements of 



danger which more often are associated with small initial 



stability. "There is not the least doubt, however, that a 



very small initial stability given to many modern mercan- 



