68 Troeejfesfor maiing Steel. 



on acpount of the great furface they prefent to the air. And when fteel is wanted, they 

 are more readily fufed, and fink beneath the fcorioe, which prevents the charcoal of the 

 iron from being confumed by the adtion of the air. On the contrary, they abforb what 

 might have been wanting from the lining of the veflel, which is prepared in fuch a man- 

 ner as to fupport itfelf without being confumed through the whole of the operation. 



When the fteel has congealed in the furnace, it is taken out and divided into feveral por- 

 tions more or lefs confiderable, which are carried to the hammer. Here a feparation is 

 made of fuch portions as are not reduced into fteel, but iron, and which occupy the fur- 

 face of the pieces. Each piece is drawn out into bars, which are reduced into other 

 fmaller bars of different dimenfions, by feparating the fofteft parts from thofe which arc 

 more hard. 



For fteel of a fuperior quality, feveral bars of the foft and hard kinds are united by 

 welding and forging. The hardeft are placed in the middle. 



We have fliown that, in order to obtain fteel from crude iron, it is neceffary to have an 

 iron abounding with coal ; but there is an excefs which is hurtful. The black crude iron, 

 which contains too much coal, affords a fteel fo brittle as to be of no ufe. This kind of 

 fl;eel becomes fixed with more difficulty than good fteel. When the workman perceives 

 this fymptom, he may prevent the bad effect by adding a certain quantity of old iron 

 fragments, which deprives the too fteely metal of its excefs of coal, and, by incorporating 

 with it, produces an uniform mafs of good fteel. When the crude iron is of fuch a na- 

 ture as to afford brittle fteel, it is ufual to mix in the refining furnace a quantity of another 

 kind of crude iron, which may modify its quality. 



Though iron and fteel are diftinguifliable by very ftrlking qualities, there is, neverthelefs, 

 a point of contact at which they are confounded : the fofteft fteel may be confidered as a 

 very hard iron, and, in faft, the feveral kinds of iron differ in hardnefs by the fame prin- 

 ciple which conftitutes fteel. They all retain a fmall portion of charcoal, which efcapes 

 the operation of refining. Thofe which contain the leaft are under like circumftances 

 more flexible, foft, duiftile, and fufceptible of acquiring by the a£tion of the hammer that 

 fibrous form which conftitutes what is called the grain of iron. Hence it is that different 

 kinds of bar iron are fometimes obtained from the fame crude iron, though the operation 

 is apparently the fame- It i^ fufficient for this effe£t that the inclination of the tuyer be 

 changed. 



Concerning Steel obtained by Cementation. 



THE fteel of cementation is formed by means of a cement, with which bars of forged 

 iron are furrounded in a cafe difpofed in the middle of a furnace, where they arc fubjeded 

 to a ftrong heat. 



We muft repeat that the good quality of the iron is a condition indifpenfable for obtain- 

 ing good fteel. It is of importance to choofe the heft kind ; and ^e Englifh, who almoft 

 cxclufively prepare the fteel of cementation, retain for that objeft all the iron of Roflagia, 

 which is the beft iron of Sweden, and for which they pay a high price. 



It is not enough that the iron (hould contain no noxious principle. It is alfo neceffary 

 that it (hould be forged with care, and its parts well united. For if it contain flaws or 



clefts 



