MAGIC OF KRUPP'S PLATES.

Dominion, Volume 6, Issue 1722, 12 April 1913, Page 15

MAGIC OF KRUPP'S PLATES.

$ THE ARMOUR OP TO-DAY. Broadside armour is by far tho most important feature m the defensive arrangement of any warship. It means tho pvotection of her engines, boilers, aiid magazines against the direct impact of projectiles delivered at her broadside, which manifestly presents tho greatest expanse of target to an enemy's gunfire. Formerly only s. certain section of tho broadsido was belted with arinouT plating, leaving tho extremities of tho ship unprotected, as being tho least vulnerablo portions of her 'hull. But the modern idea is to carr l *' the armour from end to end, maintaining tho greatest uniform thickness along that central section cf tho vessel which encloses her mcchauism anil magazines, and tapering it off at tho extremities. Thus tho battleships of tho Dreadnought type are protected with > a belt of Krupp steel, 11 inches thick in its stoutest part, graduated to G inches thick at tho forward cnd,_and I inches thick at the after end. Tho evolution in tho resisting powers of armour is most 'interestingly shown by tho varying thickness of the broadsido belting of different periods Without going back £o far as the days of simple wrought iron, wo find a that tho Trafalgar, of 18S7, was built with a partial compound bolt 230 fosi long, tapering from 20 inches in its stoutest part, to 1G inches. The weight of thi-; vessel's armour alone was 4230 tons, or substantially moro than one-third of her total displacement. Compound armour, it may be explained, consists of a wrought iron plate artifically attached to a steel face of about half its own thickness j tlij result .being; a plate with the hardness of steel on the face and tho toughness of wrought iron at the back, tho combination being designed to break up a projectile without cracking tho plate. But tho rapid improvement in navil guns reniored it essential that the invulnerability of armour shcukl be increased without a relative addition to the already terribly ponderous weight of it. The Harvey process was tho first step in this direction. This armour is estimated to have a figare of merit of 2 as against 1.25 for compound u':mour. The Majestic class was the first group of battleships to be thus armoured, their broadsido belting c&nsisting of 9 inches of Harveyed steel. In tho succeeding battleship class—the Canopus batch of 1807 —Krupp armour was first employed, and, wifc-i slight mcdifijations in tho process of manufacture, still furnishes tho protective element in warships. The steel for. tho Krupp process has a high tensile strength, approaching 50 tons par square inch, and contains small proportions of nickel, chromium, and mangaueso. ICrupp plates have a figure of merit of about 2.5 in the ratio given, above. Therefore the 11 inches of Krupp steel of ths Dreadnought type of