Withy. — On the Stability of Ships. 665 



righting-lever at any angles intermediate to those actually cal- 

 culated, and, by multiplying each by the displacement, get an 

 expression of stability in foot-tons at each angle. • If this pro- 

 cess were applied to several vessels of different types we could, 

 by a comparison of their respective curves, judge of the varia- 

 tion in, and relative values of, their stability. Some of them 

 might possess a small, some a large, and others a medium 

 range of stability. Some might show that they rapidly 

 attained to a considerable amount of stability, and then went 

 on increasing very gradually. Others, by a steady progression, 

 might increase up to a very large angle. Others, again, might 

 reach their maximum at 30° or 40° of heel, and then steadily 

 diminish. Please observe the line on the diagram (PL L.) 

 which represents the curve of stability of H.M.S. " Captain." 

 This vessel steadily gained up to 21° — a very small angle. 

 From this point her stability fell steadily, until at 54° it van- 

 ished altogether. A reference to her midship section readily 

 explains the reason of this. You will see that, owing to the 

 low free-board, the gunwale reaches the water at only 14° of 

 heel. The triangle of immersion tben begins to lose its area at 

 its broadest end very rapidly, and the width of the water-line 

 decreases with each angle of heel. The result is that the centre 

 of buoyancy, after moving satisfactorily to leeward up to 17°, 

 does so more slowly up to 21°, and then actually retraces its 

 steps, until at 54° it has come back to its starting-point, when 

 the vessel was upright, and is found perpendicularly below the 

 centre of gravity of the vessel. The slightest additional puff of 

 wind will then, owing to meeting with no resistance, cause her 

 to capsize. The width of the respective water-lines referred to 

 is as follows : When upright, 53ft. ; at 14°, 54ft. ; at 21°, 48ft. ; 

 and at 54°, 35ft. The low freeboard, resulting in a great 

 reduction of her range of stability, while at the same time she 

 ■was fully rigged, was the cause of the loss of this valuable 

 ship and of many lives. 



A great difference of opinion formerly existed as to the 

 relative advantage of a good beam or of a high freeboard 

 in affording a large range of stability. In 1871 Mr. Barnaby 

 read a paper which finally settled the controversy in favour of 

 the high freeboard. I can give you ocular demonstration of 

 several facts in stability, but will at the moment only show 

 by experiment the case of the " Captain." This model is 

 accurately made from the vessel's lines. It is weighted so 

 as to draw the same water as the ship did when starting on 

 her fatal cruise. Moreover, the centre of gravity of the model 

 corresponds in position with that of the actual ship. When I 

 hook this cord into the eyebolt in her side, and steadily cause 

 her to list, you will see how soon her gunwale becomes 

 immersed. It takes a fair amount of force to careen her at 



