IRON 937 



modified at pleasure ; for, by using much of the siftings, and making the tuyere dip 

 towards the solo of the hearth, iron is the chief product ; but if the operation be con- 

 ducted slowly, with a small quantity of siftings, and an upraised tuyere, the quantity 

 of steel is more considerable. This primitive process is favourably spoken of by 

 M. Brongniart. The weight of the lump of metal varies from 200 Ibs. to 400 Ibs. As 

 the consumption of charcoal is very great, amounting in the Palatinate or Rheinkreis 

 to seven times the weight of iron obtained (though in the Pyrenees it is only thrice), 

 the Catalan forge can be profitably employed only where wood is exceedingly cheap 

 and abundant. 



In smelting and refining by a continuous operation, three different stages may be 

 distinguished : 1. The roasting of the ore to expel the sulphur, which would be less 

 easily separated afterwards. The roasting dissipates likewise the water, the carbonic 

 acid, and any other volatile substances which the minerals may contain. 2. The de- 

 oxidisement and reduction to metal by exposure to charcoal or carburetted vapours. 

 3. The melting, agglutination, and refining of the metal to fit it for the heavy hammers 

 where it gets nerve. There are several forges in which these three operations seem 

 to be united in a single one, because, although still successive, they are prac- 

 tised at one single heating without interruption. In other forges, the processes are 

 performed separately, or an interval elapses between each stage of the work. Three 

 systems of this kind are known to exist: 1. The Corsican method; 2. The Catalan 

 with wood charcoal ; and, 3. The Catalan with coke. 



The furnaces of Corsica are a kind of semicular basin, 18 inches in diameter, 

 and 6 inches deep. These are excavated in an area, or a small elevation of masonry, 

 8 or 10 feet long by o or 6 broad, and covered in with a chimney. This area is quite 

 similar to that of the ordinary hearths of our blast-furnaces. 



The tuyere stands 5 or 6 inches above the basin, and has a slight inclination down- 

 wards. In Corsica, and the whole portion of Italy adjoining.the Mediterranean shores, 

 the iron ore is an oxide similar to the specular ore of the Isle of Elba. This ore con- 

 tains a little water, some carbonic acid, and occasionally pyrites, but in small quantity. 

 Before deoxidising the ore, it is requisite to expel the water and carbonic acid com- 

 bined with the oxide, as well as the sulphur of the pyrites. 



The operations of roasting, reduction, fusion, and agglutination are executed in the 

 same furnace. These are indeed divided into two stages, but the one is a continuation 

 of the other. In the first, the two primary operations are performed at once : the 

 reduction of a portion of the roasted ore is begun at the same time that a portion of 

 the raw ore is roasted : these two substances are afterwards separated. In the second 

 stage, the deoxidisement of the metal is continued, which had begun in the preceding 

 stage ; it is then melted and agglutinated, so as to form a ball to be submitted to the 

 forge-hammer. 



The roasted pieces are broken down to the size of nuts, to make the reduction of 

 the metal easier. In executing the first step, the basin and area of the furnace must 

 be lined with a brasqiie of charcoal-dust, 3, 4, or even 5 inches thick : over this brasque 

 a mound is raised with lumps of charcoal, very hard, and 4 or 5 inches high. A 

 semicircle is framed round the tuyere, the inner radius of which is 5 or 6 inches. 

 This mass of charcoal is next surrounded with another pile of the roasted and broken 

 ores, which must be covered with charcoal-dust. The whole is sustained with large 

 blocks of the raw ore, which form externally a third wall. 



These three piles of charcoal, with roasted and unroasted ore, are raised in three 

 successive beds, each 7 inches thick : they are separated from each other by a layer 

 of charcoal-dust of about an inch, which makes the -whole 24 inches high. This is 

 afterwards covered over with a thick coat of pounded charcoal. 



The blocks of raw ore which compose the outward wall form a slope ; the larger 

 and stronger pieces at the bottom, and the smaller in the upper part. The large 

 blocks are sunk very firmly into the charcoal-dust, to enable them better to resist the 

 pressure from within. 



On the bottom of the semicircular well formed within the charcoal lumps, kindled 

 pieces are thrown, and over these, pieces of black charcoal ; after which the blast of 

 a water-blowing machine (trompe} is given. The fire is kept up by constantly throw- 

 ing charcoal into the central well. At the beginning of the operation it is thrust 

 down with wooden rods, lest it should affect the building ; but when the heat becomes 

 too intense for the workmen to come so near the hearth, a long iron rake is employed 

 for the purpose. At the end of about 3 hours, the two processes of roasting and 

 reduction are commonly finished : then the raw ore no longer exhales any fumes, and 

 the roasted ore, being softened, unites into lumps more or less coherent. 



The workman now removes the blocks of roasted ore which form the outer casing, 

 rolls them to the spot where they are to be broken into small pieces, and pulls 

 the brasque (small charcoal) which surrounds the mass of reduced ore. 



