Engineering Wonders of the World
Volume I

THE ARMOUR OF A BATTLESHIP. 399 The first large vessel provided with armour protection in this country was the battleship Warrior, launched in 1860. This ship was built of iron, and for 218 feet of her length of 380 feet she was protected by a 4|-inch wrought-iron belt having a depth of 22 feet from top to bottom. From the Warrior period until 1874 no change was made in the quality of the armour, though it was extended over a larger surface of side in later ships, and ar- ranged so as to give protection to the ends and the rudder-head—omitted from the de- fence of the Warrior. When, as guns im- proved, the thickness of iron necessary to ex- clude the shells they fired could not be carried by the ships without detrimentally affecting their buoyancy, it became essential to dis- cover a new mode of defence. This was found in what is known as “compound” armour. Compound armour consists of a steel plate artificially attached to a wrought-iron back- ing-plate of twice its thickness, the result being a plate with the hardness of steel on its face, by which projectiles are broken up, and the toughness of wrought iron at the back, which prevents cracking taking place. At this time all the armour was concentrated along the water- line, though we, in our ships, sacrificed the pro- tection of the ends to the higher defence of the sides amidships. But the advent and rapid development of the quick-firing shell-gun rendered the large areas of unprotected sides an element of most serious danger. This involved a further advance in the man- ufacture of armour. Perhaps the most re- markable feature of the endless battle of armour v. gun is, that if at any time Harvey former leads and baffles the gun, the energies of inventors speedily improve the weapon ; whilst immediately afterwards the armour-plate manufacturers produce a plate able to withstand the new weapon; and so the fight goes on. The new material was what is known as the Harvey process armour. In this process all-steel plates are used. Animal charcoal is placed next the outer face (two plates being usually dealt with together, face to face), and the whole is then covered in with bricks and run into a gas furnace, where it remains for about three weeks, seven days being allowed for cooling. In this way the proportion of carbon on the face is increased, and the front is thus capable of being hardened. The plate is then bent to the required shape, and all necessary holes are made in its surface. It is then again heated, and the face douched with, cold water, which makes it exceedingly hard. The object to be attained is a steel plate, without welds, hav- ing such a proportion of carbon in the surface that water cooling shall produce a very hard face. The Harvey process of manufacturing ar- mour was soon superseded by the Krupp method. The steel for this purpose contains small proportions of chromium, nickel, and manganese. All Krupp Processes, plates above 4 inches in thick- ness are cemented, and are termed Krupp cemented, or K.C. The smaller plates are termed K.N.C., or Krupp non-cemented. The cementing is carried out in a fashion similar to that described above. Just a few words as to the manufacture of the steel itself. This is made from hematite pig-iron in rectangular furnaces heated by gas. In steel-making, quantities of 40 to 50 tons, or even up to 100 tons, are dealt with in each furnace charge. Pig-iron is placed on the bottom of th© chamber, together with scrap steel to the extent of about 20 per cent, of the total weight, and the charge is then thoroughly melted. Iron ore, consisting chiefly of peroxide of iron, is then thrown into the molten mass. The oxygen in the ore combines with the silicon and carbon in the pig-iron ; large quantities of gas are given off, causing a violent “ boil ” in the molten mass, and this brings every part of the metal under the oxidizing influence