334 
ARMOURED DEFENCES. 
The successful union of the steel and iron masses in these plates is 
very marked. A complete fusion seems to take place, and the natures 
of the two metals so far intermingle that it is sometimes hard fco fix 
upon an exact line where the steel ends and the iron begins. 
The degree of hardness most suitable for the steel in these plates is 
supposed to be obtained with about 0*6 per cent, of carbon. 
It is thought that the thickness of steel in a compound plate should 
be between Jth and Jrd of its entire thickness. 
III.— Description of the Principal Armoured Defences set up. 
I now come to the third and last part of the subject, which com¬ 
prises a brief description of the principal armoured works erected by us. 
The following tables give the number and nature of the guns 
for which protection has been provided, up to the present time, in each 
fort or battery at home and abroad, as well as a short description of 
the iron protection itself. 
From these it will be seen that at home 434 guns, ranging between 
the 7-ton and 80-ton, have been provided for, and abroad 91 guns 
between the 12-ton and 38-ton, making altogether a total of 525 
battering guns behind armoured walls. 
Nature of iron protection. 
No. of guns. 
Description of guns. 
Some Stations :— 
Shields in masonry work..... 
Do., do., with guns on turntables 
Iron batteries . 
Turret. 
Total . 
j Foreign Stations :— 
Shields in masonry work. 
Do., do., with guns on turntables 
Iron batteries . 
Total . 
General total. 
7 
7-in., 
7 tons. 
110 
9 „ 
12 
ft 
103 
10 
18 
„ 
42 
11 a 
25 
II 
29 
12b: 
38 
II 
2 
10 a 
18 
II 
54 
10 ,i 
18 
n 
85 
12 b> 
88 
II 
2 
16 /, 
80 
II 
434 
{ 
28 
39 
2 
9 
91 
525 guns 
9 ,< 12 „ 
30 „ 18 „ 
11 n 25 n 
\2\n 38 a 
12 hr 38 /, 
10 « 
12b . 
