81 



the Bides of his ships, which, he says, rendered them invulnerable to 

 shot and shell.* Captain Winslow, TJ. S. of the " Kearsage," indeed, 

 has replied that /the chains were not so much for defence as for protect- 

 ing the boilers and engines of the ship. This I can readily understand, 

 that it was a kind of " impromptu" defence; but that in the case of 

 steel shot or shell driven from the Whitworth hexagonal, or Armstrong 

 1 1 0-pounder, these chains would withstand its concussion, cannot be for 

 a moment believed. The law of continuity of substance forbids such a 

 theory ; for, granting the chain netting to be formed of (n) links, then, if 

 one of the series of (n) were destroyed, the law of continuity would 

 perish, and therefore the defensive force. Again, being open, the bursting 

 charges of shells would readily penetrate, even supposing the fragment 

 of the shell to fall outside the ship. 



In America it was discovered nineteen years ago that one-fourth inch 

 iron would withstand cast iron shell, and of course, then, chains of say 

 three-fourth inch would act even better; but we know that the ""Warrior" 

 target of four one-half inch rolled iron plate is no defence against steel 

 shells ; neither did the " Agincourt" target, five one-half inch, withstand 

 the immense impact of the Mackay Gun ; and it is highly probable that 

 six or seven inches of iron would offer but slight resistance to these im- 

 proved pieces of ordnance. What we really want, in my opinion, is a 

 resisting substance outside the armour plating, for we know that the 

 slightest thickness of an elastic medium increases visibly the resistance. 

 The Rev. Professor Haughton, M. D., P. E. S., has shown in his Table, in 

 connexion with armour-plated frigates, that the value of e 2 7 the square of 

 the dynamical coefficient of elasticity produced by the collision of bodies, 

 is not constant, but diminishes according to some unknown law, as the 

 velocity of the collision increases, thus : — 



Steel falling on iron with a velocity of 16 feet per sec, 



The value of e 2 = 0-2952; 

 but when the velocity increased to 40 feet per sec, 



The value of e 2 diminished to 0*2245.f 

 Hence it is apparent that, in rifled guns, the greater the initial velocity, 

 the less the value of rebound. In order to break the force thus aug- 

 mented, some intervening substance should, I think, be substituted. Cork 

 steeped in some alkali might be beneficial, as the lightness of the cork 

 and its known elastic force, with its imperviousness to flame, would ren- 

 der it of much advantage in deadening the force of impact. Soft metal 

 all along has been more successful than hard, — rigidity of substance be- 

 ing, it would seem, of rather detrimental tendency. In America cotton 

 bales are used with much advantage, being placed as we place our 

 hammocks round the gunwales, — their elastic force retarding the ve- 

 locity, and therefore decreasing the force of concussion. 



* See " Notes and Queries," August, 1862. 



f These experiments were made by dropping spherical balls of steel, iron, and brass, 

 2 \ in. diam., and measuring the height of the rebound : in this instance the weight was 

 merely influenced by gravity. 



E. I. A. PEOC. VOL. IX. M 



