METALS.
Fuel for Forge.--Dry fuel gives out far more heat than that which is damp. As a comparison of the heating powers of different sorts of fuel, it may be reckoned that 1 lb. of dry charcoal will raise 73 lbs. of water from freezing to boiling; 1 lb. of pit coal, about 60 lbs.; and 1 lb. of peat, about 30 lbs. Some kinds of manure-fuel give intense heat, and are excellent for blacksmith's purposes: that of goats and sheep is the best; camels' dung is next best, but is not nearly so good; then that of oxen: the dung of horses is of little use, except as tinder in lighting a fire.
Bellows.--It is of no use attempting to do blacksmith's work, if you have not a pair of bellows. These can be made of a single goat-skin, of sufficient power, in skilful hands, to raise small bars of iron to a welding heat. The boat's head is cut off close under the chin, his legs at the knee-joint, and a slit is made between the hind legs, through which the carcase is entirely extracted.After dressing the hide, two strongish pieces of wood are sewn along the slit, one at each side, just like the ironwork on each side of the mouth of a carpet-bag, and for the same purpose, i.e. to strengthen it: a nozzle is inserted at the neck. To use this apparatus, its mouth is opened, and pulled out; then it is suddenly shut, by which means the bellows are made to enclose a bagful of air; this, by pushing the mouth flat home, is ejected through the nozzle. These bellows require no valve, and are the simplest that can be made: they are in use throughout India. The nozzle or tube to convey the blast may be made of a plaster of clay or loam, mixed with grass, and moulded round a smooth pole.
Metals, to work.--Iron Ore is more easily reduced than the ore of any other metal: it is usually sufficient to throw the ore into a charcoal-fire and keep it there for a day or more, when the pure metal will begin to appear.
Welding Composition for iron or steel, is made of borax 10 parts, sal ammoniac 1 part; to be melted, run out on an iron plate, and, when cold, pounded for use.
Cast Steel.--A mixture of 100 parts of soft iron, and two of lamp-soot, melts as easily as ordinary steel--more easily than iron. This is a ready way of making cast-steel where great heat cannot be obtained.
Case-hardening is the name given to a simple process, by which the outside of iron may be turned into steel. Small tools, fish-hooks, and keys, etc., are usually made of iron; they are fashioned first, and case-hardened afterwards. There are good reasons for this: first, because it is the cheapest way of making them; and secondly, because while steel is hard, iron is tough; and anything made of iron and coated with steel, combines some of the advantages of both metals. The civilised method of case-hardening, is to brighten up the iron and to cover it with prussiate of potash, either powdered or made into a paste. The iron is then heated, until the prussiate of potash has burned away: this operation is repeated three or four times. Finally, the iron, now covered with a thin layer of steel, is hardened by quenching it in water. In default of prussiate of potash, animal or even vegetable charcoal may be used, but the latter is a very imperfect substitute. To make animal charcoal, take a scrap of leather, hide, hoof, horn, flesh, blood--anything, in fact, that has animal matter in it; dry it into hard chips like charcoal, before a fire, and powder it. Put the iron that is to be case-hardened, with some of this charcoal round it, into the midst of a lump of loam. This is first placed near the fire to harden, and then quite into it, where it should be allowed to slowly attain a blood-red heat, but no higher. Then, break open the lump, take out the iron, and drop it into water to harden.
Lead is very useful to a traveller, for he always has bullets, which furnish the supply of the metal, and it is so fusible that he can readily melt and cast it into any required shape; using wood, or paper, partly buried in the earth, for his mould. If a small portion of the lead remain unmelted in the ladle, the fluid is sure not to burn the mould. By attending to this a wooden mould may be used scores of times.
Fig. 1 shows how to cast a leaden plate, which would be useful for inscriptions, for notices to other parties. If minced into squares, it would make a substitute for slugs. The figure represents two flat pieces of wood, enclosing a folded piece of paper, and partly buried in the earth the lead is to be poured into the paper.