Pnetjfesfor tnailng Sttel by Cemintation. 69 



clefts within the bars, they become much more perceptible when the iron has acquired the 

 nature of fteel ; and it would not be praAicable to unite them perfc6lly, becaufe the parts 

 of Iteel arc much lefs difpofed to weld and adhere together than thofe of iron. We have 

 had convincing proofs in our own experiments, that the irons of France of good quality, 

 fuch as thofe of the ci-devant Berry, afford only a bad fteel when cemented in the ftate they 

 ufually are delivered in from the forge; but the fame iron, after having been carefully forged 

 and hammered, formed fteel equally good with that which had been made at the fame time 

 from an excellent iron of Sweden. In another experiment the fteel prepared with iron of 

 the ci-devant comte de Foix, which had been well forged, produced fteel of a quality 

 equal to that which had been obtained in the fame operation with Swedifli iron. 



Hence it refults, i. That the beft Swediftj iron owes its property of forming good fteel, lefs 

 to any particular quality of the ore than to the care with which it is forged and fubmitted 

 to the adtion of the hammers: 2. That we pofTefs in France irons capable of affording good 

 fteel, provided care be taken that they be well forged ; but the mere negle£t in this ope- 

 ration may prove fatal to a plan in other refpefts well conduced. 



The firft attention which ought therefore to be paid in the attempt to manufadture fteel 

 16 to procure good iron, to examine whether it be well forged ; and in cafe this operation 

 has not been fufficiently attended to, it muft be forged and made found before it is fub- 

 je£led to cementation. 



It has long been fuppofed that the cement proper for the fteel-making procefs ought to 

 contain faline, inflammable, fat or fulphureous parts, which were fuppofed to penetrate the 

 iron and change it into fteel. Hence have arifen many pretended fecrets, which have di. 

 verted the attention of thofe who have engaged in undertakings of this kind under the 

 guidance of ignorant pretenders. There are no fecrets in the compofition of the cement. 

 The Englifti ufe no material but the charcoal of wood reduced to powder ; and in fadl the 

 only eflential condition is, that the iron fhould become impregnated with the very fubftance 

 of the charcoal uniformly to its centre. 



When the bars or plates of iron which are to be converted Into fteel are ready for the 

 furnace, they are cut to the length of the cafe or crucible in which the cementation is to be 

 made. A bed of charcoal powder, fifted through a coarfe Ceve, and flightly wetted, is laid 

 in the bottom of the cafe. Upon this is placed a row of iron bars at a little diftance from 

 each other. This firft layer of iron is then covered with a bed of charcoal powder, which 

 fills the fpaces within the bars, and rifes to the height of half an inch above them. A new 

 range of bars is then laid and covered with charcoal as before, and in this fucceflive way 

 the operator proceeds till the cafe is full. The laft row Is covered with charcoal pow^der, 

 over which is laid a bed of fand to cover its furface entirely, and prevent its being deftroyed 

 by combuftion. The fand muft be moiftened and well preffed together in the form of a 

 roof.rifing higher than the fides of the cafe, fo as to be feveral inches thick in the middle. 



When the preparation or charging of the cafe is finiflied, the furnace is difpofed for 

 making the fire, which is gradually increafed, and muft be kept up for a longer or fhorter 

 time according to the quantity of fteel, and confequently according to the fize of the cafe. • 

 At Newcaftle, where between twenty-five and thirty thoufand weight of fteel is cemented 

 in two cafes contained in a furnace, the operation lafts five days and five nights. At. one 



of 



