IRON. 



iron is mixed in the smelting furnace with 

 combustible matter and glass, it will 

 either be completely or partially revived, 

 according 1 to the management of the pro- 

 cess- Much of the coal will however be 

 so enveloped with the vitreous matter as 

 to remain unburned : and the reduced 

 iron, with which it may be in contact, 

 will be in the same situation as forged 

 iron in the cementing pot ; that is to say, 

 it will be in contact with coal at a very 

 elevated temperature, and defended from 

 the air. From the great infusibility of 

 iron, it may reasonably be concluded, 

 that the reduced metal does not flow 

 into the bottom of the furnace, until the 

 charcoal has converted it into a fusible 

 matter similar to steel, by the same action 

 which takes place in cementation, what- 

 ever.that action may be. Hence it must 

 follow, that the various specimens of crude 

 or cast iron will differ in their qualities, 

 as well on account ofthe degree of cemen- 

 tation they have undergone, as the degree 

 of reduction which has taken place among 

 the metallic parts, which are carried 

 down, and form the whole mass. Since 

 the coal, in the process of cementation, 

 communicates or adds weight to the 

 iron; and since crude iron, as well as 

 steel, exhibits sparkles, and is more easily 

 burned than other iron; it may therefore 

 be concluded, that, in the process of re- 

 fining, that part ofthe inflammable sub- 

 stance which had united with the metal is 

 burned, and leaves the iron much less fu- 

 sible than before. Stirring the mass mul- 

 tiplies the contacts of the air with the 

 burned substances ; these surfaces of con- 

 tact will therefore successively afford thin 

 coats of infusible metal. In this manner 

 it is found, that, if a large piece of crude 

 iron be exposed to heat in a wind furnace, 

 the external part will be deprived of its 

 fusibility during the time required to pro- 

 duce a strong heat in the whole mass ; 

 and the internal part will be melted, and 

 run out, leaving the shell behind. Iron, 

 which is ofthe consistence of paste, may 

 therefore be considered, like any other 

 paste, as a mixture of a fluid with a solid. 

 It will be easily Understood, that the 

 forging will bring the parts of difficult 

 fusion together, and extrude the less re- 

 fined and fluid parts ; it will also be evi- 

 dent, that this operation is not likely tp 

 drive out the whole ofthe fusible matter. 

 When the iron has arrived at that state, 

 wherein the quantity of fibre or tough 

 iron is sufficient to answer the mechani- 

 cal purposes to which it is intended to be 

 applied, the artist will consider it as suffi- 

 VOL. VI. 



ciently refined; and the residue offusiblc 

 iron contained in the bar answers, in all 

 probability, the valuable purpose of con- 

 necting these infusible masses together. 

 Thus we find that forged iron appears as 

 if covered with a varnish, when urged to 

 a white heat ; we find that this varnish is 

 more abundant in steel , and that iron and 

 steel may be respectively welded toge- 

 ther by application in this state ; an effect 

 which it would be very difficult to account 

 for, in this most infusible of metals, if it 

 were not for such an admixture. But cast 

 steel, steel over cemented, and crude iron, 

 appear to be in the st'.te of all other metals 

 platina excepted. They cannot be welded, 

 because welding implies a partial fusion; 

 or an effect si mi Isr to the gluing or uniting 

 of solids by the application of a fluid, 

 which afterwards becomes consistent. 

 And as platina possesses this valuable 

 property, it seems reasonable to infer,that 

 it must also consist of two metallic sub- 

 stances of different degrees of fusibility; a 

 supposition that appears to be confirmed 

 by the discoveries of Dr. Wollaston and 

 Mr. Tennant. 



Crude iron, and steel of a uniform tex- 

 ture, consist therefore of a fusible combi- 

 nation of iron with the combustible sub- 

 stance ofthe coal, or something which is 

 imparted from it, the crude iron differ- 

 ing from the steel simply in being over- 

 dosed with carbon, and less pure, on ac- 

 count ofthe admixture of metallic oxide, 

 which can scarcely, perhaps, be avoided 

 in the large process. It appears, there- 

 fore, that crude iron must pass through 

 the state of steel, before it can become 

 forged iron ; and, consequently, that the 

 fabrication of steel from this last is a cir- 

 cuitous process, which can only be repaid 

 by the absence of those unreduced parts 

 which may exist in the crude iron. At 

 some forges, however, where the ore, the 

 flux, the fuel, and the management, are 

 adapted to each other, the produce af- 

 fords steel, when duly refined. At other 

 manufactories, the crude iron is either 

 refined, or converted into steel, by run- 

 ning it into thin plates, which are strati- 

 fied with charcoal, and burned in a close 

 furnace. In this way the metal is refined 

 by degrees, without undergoing fusion ; 

 and if the heat be raised to that of ce- 

 mentation, the iron will not only be re- 

 duced, but converted into steel. In the 

 forges of Carinthia, the grey crude iron 

 is also converted either into soft iron, or 

 steel, according to the management of a 

 somewhat similar process. The iron is 

 fused in a large melting' pot ; and a small 



Tt 



