Steel from one-fifth to one per cent.
Wrought iron less than one-fifth per cent.
Mild steel, which has least carbon of all the varieties of steel and in this respect is therefore nearest to wrought iron, is used for the same purposes as wrought iron, such as shipbuilding, bridges and roofs, tanks, gas-holders, etc. When the Admiralty want a specially fast ship such as a torpedo-boat destroyer with a hull as light as possible consistent with strength they have it made of steel with a slightly larger percentage of carbon so that the steel is stronger and the vessel's frame can be made lighter. The steel for shells, too, needs to be of a certain strength to give the best results, so the percentage of carbon is adjusted accordingly.
For guns themselves, again, special properties are
needed, and so not only is the carbon regulated to a nicety but other things such as nickel and chromium are added. Altogether, steel is one of the most marvellous substances known, certainly the most marvellous metal. Copper is just copper and no more, zinc is just zinc, and the same with lead, but iron (which really includes steel) can be adapted to so many purposes, can be endowed at will with so many different properties, that without doubt iron, common, plentiful iron, is the king of all the metals.
CHAPTER VIII
MORE ABOUT GUNS
As has been remarked elsewhere, some of the guns used by the soldiers in land warfare are very different from those used in the navy. The latter, being carried on the ships to which they belong, can be of those proportions which best suit their purpose. Consequently they are usually very long compared with their diameter.
The field guns used by the Royal Field Artillery are shorter in proportion to their calibre than are the big naval guns. Otherwise they would be far too long to handle in the field. They are mounted on carriages drawn by horses, and are so handy that they can go anywhere where infantry can go and can travel just as fast. It takes a very short time to get them ready for action, too, so that they can accompany infantry quite freely, neither arm impeding the movements of the other. The Horse Artillery, again, whose guns are even lighter still, can accompany cavalry, travelling as fast and coming into action almost as quickly as the troopers themselves.