PENETRATION OF IRON PLATES BY STEEL SHOT. 433 



posed. It would have been interesting to find the effect of adding one inch 

 to the armour plate and supplj-ing a |-inch iron skin. 



On the effect of Baching to Iron Plates. 



It might appear at first sight that wood backing would have the effect of 

 strengthening an iron plate ; the results, however, of a very large number of 

 cases go to prove the opposite — namely, that the backing aftbrds little, if any, 

 support to the plate, unless it be of the rigid form, such as the ' Hercules ' 

 and ' Bellerophon.' In other words, if a shot is capable of perforating an 

 unbacked 4|-inch plate, it will perforate it or break it away equally if it be 

 backed by wood alone. 



We have many instances of this. Thus we find that a steel shot fired 

 from the 68-pounder perforated 4g-inch plates on the ' Warrior,' 4|-inch 

 plates on the Small Plate, a 5-inch plate (round 960), and penetrated to the 

 same depth in 5^-inch unbacked and backed plates. 



We have evidence, however, that a rigid backing is a great advantage ; 

 this was particularly appai-ent in the case of the ' Hercules,' where the plates 

 were not perforated by some shot which struck with sufficient " work " to 

 penetrate them completely if unbacked. 



We have also evidence of the great superiority of packed backing of teak, 

 such as in the ' Warrior,' ' Minotaiu:,' &c., over the ordinary side of a line- 

 of-battle ship, and of the great support which an inner skin affords. 



Thus it required 33 foot-tons per inch of shot's circumference to penetrate 

 the backing and skin of the ' Warrior,' viz. 18 inches of compact teak and 

 a |-inch iron plate, strengthened and supported by iron ribs ; and we see 

 that 16 foot-tons per inch were sufiicient to penetrate the side of an ordinary 

 line-of-battle ship, viz. 25 inches of oak. 



We also find that the backing of the ' Lord Warden ' required 58 tons per 

 inch, and of the Small Plate target about 16 tons per inch. This shows the 

 vast superiority of compact backing supported by internal iron plates. 



Resume of tJie Conclusions which may be drawn from the experiments against 



iron, 



1. "\i\Tien it is required to perforate the plate, the projectile should be of 

 a hard material, such as steel or chiUed iron. 



2. The form of head best suited for the perforation of iron plates, whether 

 direct or oblique, is the pointed ogival. 



3. The best form of steel shell is that in which the powder can act in a 

 forward direction, and which is furnished with a solid steel head in the form 

 of a pointed ogival. 



4. When chilled iron can be made of the best quality, it is almost, if not 

 quite, as effective as steel for solid shot. And where the projectile can per- 

 forate with ease, the chilled shot is more formidable than steel, as it enters the 

 ship broken up, and would act as grape *. 



5. To attack well-built iron-clads effectively, the guns should be, if pos- 

 sible, not under 12 tons weight and 9 inches calibre, firing an elongated 

 projectile of 250 lbs. with about 40 lbs. of powder. 



6. When the projectiles are of a hard material, such as steel, the perfora- 

 tion f is directly proportional to the " work" in the shot, and inversely pro- 

 portional to the diameter of the projectile ; and it is immaterial whether this 



* The introduction of chilled iron is due to Major Palliser, who has devdted much 

 time and attention to the subject. 



t Or power of complete penetration. 

 1866. 2 F 



