202 



NATURE 



\7tdy 12, 1877 



the ship safe even when she had only the stability shown 

 by b, the ship actually capsised when she had the lirger 

 amount shown by curve a, the two curves being the same 

 up to about 20 deg. of incliniition, but the latter showing 

 much greater stability both in amount and in range after 

 that amount of inclination was passed. Mr. Barnes no 

 doubt expected that the ship would never be pressed 

 under canvas enough to endanger her, but the event 



E^. 1 



showed that in matters of this kind the measure of safety 

 must be ample, and that we must not trust to the chapter 

 of accidents for the security of our men-of-war against 

 capsising. 



We are now in a position to explain the case of the 

 Iii/iextble up to the piint at present attained in the dis- 

 cussion, but in order to understand it the reader must 

 take clearly into his mind certain differences between her 



Typical Curve? of Slatic.il Stability, 



Tiii.2 



and all previous ships as regards the relations of the 

 armoured and unarmoured parts. In the case of the 

 Captain we had a ship with armour rising to a uniform 

 height of six feet above the water from stem to stern, and 

 above this armour at one end a forecastle and at the 

 other end a poop, both of these being of thin iron and 

 unarmoured. It was in view, no doubt, of these un- 

 armoured ends being liable to be so injured in action 



as to contribute nothing to the ship's stability that the 

 Admiralty officers calculated and stated (as above quoted 

 from Mr. Barnes' report) the ship's stibility with the poop 

 and forecastle destroyed. But the reader shoald carefully 

 observe that as thes; unarmoured ends were wholly 

 situated in the Captain at a height of s'x feet abovi the 

 water, their destruction to any extent whatevir could not 

 affect the ship's stability at smiU angles of inclinition ; 

 and in point of fact by looking at the dotted 

 curves in Fig. 2 we see that the stability is 

 the same whether these ends exist intact or 

 not up to an angle of about 22 deg., for up 

 to that point the two curves are identical. 

 At that angle of inclination the poop and 

 forecastle enter the water, and the curve of 

 stability declines much more rapidly when 

 they are injuied than when they are unin- 

 jured. In the cases of the Devastation, 

 Tlmnderer, and some other ships, there was 

 a different arrangement, and one less favour- 

 able to stability, for in them the forecastle 

 (not the poop) was sunk, so to speak, down 

 into the armour, so as to reach to within a 

 foot or two of the water's surface. In such 

 cases, of course, the curve of stability, with 

 the unarmoured ends injured, begins to 

 decline earlier than if the forecastle stood wholly above 

 the armoured side as in the Captain's case ; but the 

 Devastation class are all unmasted ships, and therefore 

 subject to no pressure of canvas, so that much less 

 stability was required in them than in the Captain and 

 other rigged ships. 



The Inflexible class of vessels differ from all the ships 

 previously named in a very marked manner, for in her 

 the ends are entirely unar- 

 moured (excepting as regards 

 a horizontal deck lying seven 

 feet below water), and while 

 the forecastle, and poop, where 

 it exists, in the other ships 

 named are comparatively 

 short, in her they occupy 

 two-thirds the length of the 

 ship — one-third at each end. 

 The central part of the ship, 

 one-third in length, is alone 

 armoured with side- armour, 

 and therefore in considering 

 the stability during an action, 

 we may suppose that two- 

 thirds of the ship's length, 

 viz., the two wholly unar- 

 moured ends, are destroyed, 

 destroyed that is in the sense 

 "^ in which Mr. Barnes obvi- 

 ously used the phrase in the case of the Captain; or, in 

 other words, so broken and damaged by shot or shell as to 

 let the sea flow freely in and out of them, and therefore to 

 possess no stability to help in keeping the ship upright. In 

 Figs.3 and 4 wc have, illustrated, the /«//,uv7V<- injured in 

 this manner. One of the contentions of the Admiralty is 

 that these ends cannot be injured during an action to this 

 extent ; but whatever the Admirahy officers may now 



