434 REPOKT — 1866. 



"work" be made up of velocity or weight, within the usual limits which 

 occur in practice. 



7. The resistance of wrought-iron plates to perforation by hemispherical- 

 headed steel projectiles varies as the square of their thickness. 



8. Hitting a plate at an angle diminishes the eifect as regards power of 

 perforation in the proportion of the sine of the angle of incidence to unity. 



9. The resistance of wrought-iron plates to perforation by steel shot is not 

 much (if at all) increased by backing simply of wood ; it is, however, much 

 increased by a rigid backing, either of iron combined with wood, or of granite, 

 iron, brick, &c.* 



10. Iron-built ships, in which the backing is composed of compact oak or 

 teak, offer much more resistance than similarly clad wooden ships. 



11. The best form of backing seems to be that in which wood is combined 

 with horizontal plates of iron, as in the Chalmers, ' BeUerophon,' and 

 ' Hercules' targets. 



12. An inner iron skin is of the greatest possible advantage; it not only 

 has the effect of rendering the backing more compact, but it prevents the 

 passage of many splinters which would otherwise find their way into the ship. 



No ii'on-clad, whether iron-built or wooden converted, should be without 

 an inner iron skin. 



1 3. The bolts known as " Palliser's bolts," are the best for securing ar- 

 mour plates. 



In these bolts the diameter of the shank is reduced, so that it is less than 

 the diameter at the screwed end. 



In the foregoing pages great stress has been laid on penetration. 



There are two methods by which an iron-clad vessel can be destroyed by 

 the fire of artillery. 



1. Rachiny t, or the impact of heavy shot of large size moving at low 

 velocities, and intended to shatter the vessel's armour, and by repeated 

 shakes ultimately to knock the whole structure to pieces. 



2. Punchiny J, or the penetration of the vessel's side either by elongated 

 shot or shell, intended to kill the crew, damage the machinery, and sink the 

 vessel by holes made through her, at or near the water-line. 



Both these systems have their advocates, and there is undoubtedly a great 

 deal to be said on both sides. 



All warlike operations tend to the crippling of your enemy ; and that 

 system is evidently the best which will cripple him in the shortest time, 

 in the easiest manner, and at the least possible expense. 



Now time is an element which will largely enter into consideration in 

 future actions with iron- clad vessels. 



Suppose two opposing iron-clads to meet, one armed with guns on the 

 "racking" system, the other with guns on the "punching system;" it is 

 probable that the vessel which could send her shot clean through the sides of 

 her adversary would have the greatest chance of reaching a vital part in a 

 given time. Besides which, a " punching " shot is usually an elongated rifle 

 projectile, animated by a moderately high velocity, and has consequently a 

 flatter trajectory than the "racking" shot, which travels at a low velocity; 

 and as accuracy and a flat trajectory are closely allied, the " punching " 



. * That is to say, a shot which is capable of breaking a hole through a 4-5-inch plate 

 unbacked, will be also capable of doing so if the plate be only backed by wood, to the 

 extent that, were the plate taken off the backing, the piece of iron where the shot had 

 struck would fall out. 



t American system. \ English system. 



