216 Prof. F. El gar. The Variation of 



The curve of stability, as thus constructed, has been in common 

 use at the Admiralty, and in a few of our leading mercantile ship- 

 yards for some years. The loss of H.M.8. " Captain," by capsizing at 

 sea, furnished the impetus which led to the practice of producing 

 stability information in this complete and instructive form, becoming 

 established at the Admiralty. Many losses have occurred of late 

 years in the mercantile marine from a similar cause, and forcibly 

 directed the attention of mercantile naval architects to the same 

 point. Curves of stability have been constructed for large numbers of 

 vessels of various classes, many of which have been published ; and the 

 general character of a ship's stability can now be judged of with 

 much greater accuracy than was possible a few years ago. It 

 appears that prior to 1867 no calculations had been made which 

 s ho wed how the stability of a ship became affected by inclining her till 

 the water-line came up over the deck ; or at what angle the stability 

 vanished. Messrs. John and White say in the paper before referred to: 

 " The metacentric stability, as it was termed, was by general consent 

 taken as a sufficiently good standard of comparison, and no approxi- 

 mation was made, nor any great importance attached to the angle of 

 inclination when a ship ceased to be stable. It was very generally 

 known that up to very considerable angles of heel, the stability of 

 high-sided ships continued to grow, even more rapidly than it 

 appeared to do from the metacentric method, and the vague impression 

 that the angle would be very large at which the ship became unstable, 

 was considered sufficient to render investigation needless." 



The investigations conducted at the Admiralty into the stability 

 of war-ships of low freeboard, and those made by naval architects 

 outside of the Admiralty into the condition of deeply laden merchant 

 steamers of low freeboard and with high centres of gravity of cargo, 

 prove that the mere application of the metacentric method may 

 often lead to a false sense of security being established respecting the 

 stability of certain types of vessels. 



H.M.S. " Captain " had a metacentric height of about 2| feet when 

 laden, which in the absence of definite information, at that time 

 most unusual and not considered absolutely necessary, respecting the 

 righting moments at large inclinations, and the angle at which the 

 stability vanished was not supposed to be insufficient. Some of our 

 low freeboard monitors and deeply laden merchant vessels with flush 

 decks and low freeboards, have metacentric heights which, by them- 

 selves, furnish no clue to the rapidity with which the stability 

 diminishes after a moderate angle of inclination has been passed ; or 

 the smallness of the angle at which it vanishes. The introduction of 

 curves of stability, and the extent to which they have been applied 

 in practice, have led to a due and precise appreciation being formed, 

 by many, of the dangers attendant upon low freeboard. The 



