ARMOUR AND ITS ATTACK BY ORDNANCE. 
171 
thick) should be insisted on as showing that fazed shells of any kind 
can be made to burst from 1 to 10 feet behind the thinnest ship’s side. 
It may also be convenient to note the following rough guide as to 
the structural strength of projectiles and the limit to their possible 
perforation. Common cast-iron shells will perforate and carry fire 
through wrouglit-iron half a calibre thick. Armour-piercing steel 
common and Palliser shells will perforate and carry fire through 
ordinary steel or steel-faced armour one calibre thick. Forged steel 
projectiles easily get through wrought-iron armour up to two calibres 
thick, which is also about the present limit of the muzzle energy of many 
of the B.L. guns. As before said a Holtzer 6-inch shot has per¬ 
forated 17 inches of iron easily, but 4*7-inch forged steel Laboratory 
and Projectile Company shot broke against 12 inches of wrought-iron. 
This last estimate, then, is given only to enable a general guide to be 
conveyed by the series. Common shell, half a calibre ; “ armour- 
piercing common,” one calibre; and armour-piercing shot, two calibres. 
As to perforation achieved within the above limits, the old rule of 
thumb of one calibre perforation for each thousand feet velocity was 
}fr 
good for projectiles whose approached 04 fired with velocities below 
. . IF . 
2000 f.s. If applied to projectiles, of which the is very large, as in 
the 10-inch and 13’5-inch B.L., where it reaches 0*5 or to velocities 
much exceeding 2000 f.s. a considerable error arises. 
Systematic instructions and information as to armoured ships can 
only be given in connection with Coast Defence. It may, however, be 
well to suggest a few principles to keep in view in dealing with foreign 
armoured ships in their latest forms. The figures for this purpose are 
taken from the paper read at the Institution of Naval Architects by 
Mr. White, the Director of Construction to the Admiralty in 1889. 
Until quite recently ships were armoured on one of two plans, speak¬ 
ing generally, which, for the sake of distinction, may be termed the 
English and French plans. On the former the ship was very strongly 
protected amidship and the ends left without vertical armour, the lower 
parts and floating power of the vessel being protected by a horizontal 
armoured deck. [See Inflexible, Fig. 31.) 
Fia. 31.— ( 'Inflexible). 
The French plan is to insist on a complete armoured belt at the 
water-line extending from stem to stern, as well as a horizontal 
23 
Rule as to 
limit of per- 
foration of 
projectiles. 
General 
plans of 
ships’ 
structures. 
