Iron ores are easily reduced by heating them in direct contact with burning fuel

A lump of ore put into a blacksmith's forge is quickly reduced. The particles of pure iron resulting, however, only become pasty at the heat of a forge, and the temperature is also not high enough for the iron to combine with the carbon of the fuel and form cast-iron. There results, therefore, a spongy ma of highly heated particles of pure iron, which can be taken out of the forge and rapidly welded by hammering into a solid lump or bar of soft iron. This is the principle of the ancient methods of obtaining iron as used among all peoples, and even now not extinct in many countries. The Catalan. Forge, shown in Fig. 1, is a good type of these forges for the direct production of wrought iron from iron ore; it was in use in the Pyrenees until recent times. A cavity (c, d) is lined with bricks, and filled with fuel mixed with iron ore. A blast of air is conveyed by the air-pipe T and discharged through the nozzle N. The apparatus on the left is a trompe, or water blast, in which the falling IMG:content-0808.png:[graphic] column of water B draws air through the openings g, g, and thus furnishes air pre ure in the box E. Such an arrangement is suitable in mountainous countries, where waterfalls abound. In such a forge, a charge would be worked in six hours, producing 300 lbs. of iron. When the reduction is complete, the spongy ma is lifted out of the hearth and welded by rapid hammering with tilt-hammers into bar iron. If such a forge were worked extra hot, with plenty of fuel, the iron would absorb a small amount of carbon, and rather hard steely iron sometimes result. In Germany and England a sort of stack or chimney was built over the hearth into which the charges were placed to be heated up before entering the hearth by the hot gases rising from the hearth. With this arrangement, coupled with an increase in the size of the hearth, the temperatures in these hearths reached ab. 1350° C., the point at which iron absorbs sufficient carbon to form cast-iron. The "high ovens" of Germany and "high forges" of England thus developed into the modern blast-furnaces; for when once the usefulne of cast-iron had been tested, the sizes of the furnaces were rapidly increased to meet the demand.