456 
PRINCIPLES Of GUNNERY, 
Steel. 
turret ships this is important, as armour-plates can be made of a 
breadth equal to the height of the turret,, and through joints can thus 
be dispensed with, the bolting and securing of the structure is faci¬ 
litated, and the absolute cost is less. 
Armour-plates made of steel have some very important advantages 
which point to the advisability of employing steel instead of wrought- 
iron, either partially or entirely, for defensive purposes. Steel plates 
have a greater absolute tenacity, and more perfect homogeneity of 
structure than wrought-iron plates. They have also a greater resist¬ 
ance to penetration. This latter is of great importance, as it becomes 
possible by the use of steel armour to prevent ships* sides being 
punched or perforated by means of the heaviest gun yet made.. There 
is, however, a great disadvantage which renders steel armour more 
susceptible of succumbing under the system of demolition by racking 
— i.e., a crystalline structure which makes it liable to crack under rela¬ 
tively light blows; so that by repeated blows from medium guns the 
demolition of the steel plate is certain. 
Experiments carried out by the Italian Government at Spezia in the 
autumn of 1876 with the 100-ton gun proved conclusively the value 
of the Schneider steel plates over wrought-iron plates of the same 
thickness. The Schneider steel target, which successfully resisted the 
100-ton gun, striking with an energy of about 589 ft. tons per inch of 
circumference, consisted of a solid plate of soft hammered steel 22 ins. 
thick (vide figure), supported by two layers of wood backing—one 
vertical, the other horizontal. The wood backing was again supported 
by an iron plate T5 in. thick, and behind this again by the vertical 
frames of the ship, supported by the proper deck beams, those above 
being iron, and bent down to meet the ground at an acute angle; thus 
gaining the support which would be given by the other side of the 
