332 
ARMOURED DEFENCES. 
forged steel shell in oblique bitting, but in this latter mode of attack 
on steel, all steel projectiles that have been yet tried have gone to 
pieces. 
Steel-faced armour completely baffles chilled cast-iron projectiles. 
For direct fire, the longer the head of the projectile the greater will 
be the effect on iron armour, but in oblique fire the best effect has 
been produced with heads struck to a radius of two diameters of the 
shots body. 
As I have already said, flat heads are much inferior to pointed heads 
in both direct and oblique fire. 
II.— Account of the Materials used for Armour and their 
Manufacture. 
Manufac. Beginning with wrought-iron armour :—For this, as made at Sheffield, 
w/ought. H ie hest cold-blast pig with a proportion of Cumberland hasmatite is 
iron armour generally used. Roughly speaking, it takes 2 \ tons of pig, or 2 tons 
11 of ball furnaced iron—that is, of puddle ball—to make 1 ton of finished 
armour plate, and in the last heating of all, when the iron is in a very 
costly state, there is a loss by the actual burning away of the iron of 
about 10 per cent. It takes also about 6J tons of coal to make a ton 
of armour. 
Perhaps the shortest way of giving an account of the manufacture 
of rolled iron armour will be to say how some one plate in particular 
has been made, and I will select for this purpose one of the heaviest 
ever produced. 
This was one of the 8-in. plates made for the target to test the 
80-ton gun at Shoeburyness. Its finished dimensions were—length 
16 ft., width 10 ft., and its weight 23 tons. 
For its manufacture 1170 slabs 30 ins. long, 12 ins. wide, and 1 in. 
thick were made from the puddled ball and bar. These were piled, 
furnaced, and rolled into 65 plates about 5 ft. square and from 1 in. 
to l-|in. thick, called small moulds. These, again, were piled and 
rolled into quarter-moulds, and the quarter-moulds into armour-plate 
moulds, and the pile for the last rolling was made up of three moulds 
about 10 ft. square, two of 7-in. and one of 3-in. thickness. As they 
entered the furnace for this last heating they weighed about 35 tons; 
as they came out after about 12 hours they weighed 31 \ tons. 
They were rolled down in the last rolling from 17 ins. to 8 ins.; so 
that, in a certain sense, this plate may be said to have been made by 
rolling a column of iron nearly 100 ft. high down to one only 8 ins. 
high. The fibrous character of a plate depends largely upon the 
amount of reduction in the last rolling. 
The rolls are plain cast cylinders; those used in the present case 
are about 3 ft. in diameter, 12 ft. long, and each one of the pair weighs 
nearly 20 tons. They are driven by very powerful steam machinery, 
and made to reverse their running, so that the plates are sent through 
one way and then back again, and so on, the rolls being brought 
nearer together each time, until the plate is brought down to the 
required thickness. 
The specific gravity of a good iron armour plate is about 7'625* 
