IRON. 



ness by being ignited, then laid on a plate 

 of cold lead, and suddenly covered with 

 another plate. These would be unequally 

 hardened, and bend, if plunged in water. 



The bhdn^ of steel appears to effect its 

 elasticity in a manner not easily explain- 

 ed. This operation consists in exposing 

 steel, the surface of which has been first 

 brightened, to the regulated heat of a 

 plate of metal, or a charcoal fire, or the 

 flame of a tamp, till the surface has ac- 

 quired a blue colour. No\v, if this blue 

 coal be removed by grinding, theelastici- 

 ty is completely destroyed, and may be 

 restored by bluing the steel again. Rub- 

 bing with sand or emery-paper, glazing, 

 or burnishing, equally impairs the elasti- 

 city, in proportion as it destroys the blue 

 coat. Saw-makers first harden their plates 

 in the usual way, in which state they are 

 brittle and warped ; they then soften them 

 by blazing, which consists in smearing 

 the plate with oil or grease, and heating it 

 till thick vapours are emitted, and burn off 

 with a blaze ; and after this they may 

 be hammered flat ; lastly, they blue them 

 on a hot iron, which renders them stiff 

 and elastic, without alteringtheirflatness. 



The Damascus sword blades have long 

 been celebrated for their excellence, but 

 it is not known how they are made. Mr. 

 Stoddart took six small bars of good mal- 

 leable iron, and the same number of sheer 

 steel ; laid them alternately on each 

 other ; welded them together ; forged 

 them into a stout flat plate, which was 

 twisted spirally into a cylinder, hammer- 

 ed fiat, and again welded-, hammered 

 this flat, doubled it throughout its length, 

 inserted in the fold a slip of good steel to 

 form the edge, and by another welding 

 heat consolidated the whole into one 

 mass. This being forged to a proper 

 shape, cracked in different places on be- 

 ing cooled in water after heating; but 

 Mr. Stoddart conceives, that, by using 

 more pieces, repeating the twisting, and 

 not quenching in water, the process 

 would succeed. 



Every species of iron is convertible in- 

 to steel by cementation ; but good steel 

 is not to be made except from iron of the 

 best quality, which possesses a certain 

 stiffness and hardness as well as mallea- 

 bility. Swedish iron, as we have before 

 remarked, is the best for this purpose. 

 M. Duhamel tried a great number of the 

 irons of France, Sweden, and Spain. He 

 found the second to be the best ; but he 

 likewise obtained excellent steel, superi- 

 or to those of Styria and Carinthia, which 

 are the best German steels, by using cer- 



tain iron made in France. But this iron 

 was selected without fault ; and, in some 

 instances, theloup or piece at the smelt- 

 ing furnace was fused and forged a se- 

 cond time ; a process, which, though at- 

 tended with loss of weight and additional 

 expense, he recommends as absolutely 

 necessary for making steel iron from ores 

 of indifferent quality. The white spa- 

 those iron ores afforded him the best 

 iron for the purpose of cementation ; 

 and these also are the ores which afford 

 the best steel by fusion in Styria, Carin- 

 thia, and Tyrol. He informs us that the 

 English use no other cement than mere 

 charcoal, which he also finds perfectly 

 adequate to the purpose ; and, moreover, 

 that the quality of the steel is not affect- 

 ed by the different kinds of charcoal 

 made use of. He remarks, nevertheless., 

 that it may be advisable to add from one- 

 fourth to one-third of wood ashes, espe- 

 cially where the iron is not of so good a 

 quality as to afford steel possessing tena- 

 city of body, as well as hardness. These 

 ashes, which he used with success, pre- 

 vent the steel-making process from being 

 effected as rapidly as it would otherwise 

 be, and give the steel pliability, without 

 diminishing its hardness. It is remarked, 

 that, in the case of this management, the 

 blisters on the surface of the steel arc 

 smaller and more numerous. He like- 

 wise tried sea-salt. Fifty pounds of salt 

 are sufficient for a furnace of steel of 

 twelve thousand weight. The salt is 

 pulverized, and sprinkled on the bars of 

 iron when put into the furnace. He 

 found that this ingredient likewise con- 

 tributes to give body to the steel. In the 

 arrangement of the bars in the furnace, 

 the cement is laid one inch thick at the 

 bottom, and half an inch thick between 

 each layer of iron. Our author affirms, 

 that the process would succeed equally 

 well, if the thickness were a little more 

 than a quarter of an inch. The thickness 

 of the bars of iron is indifferent, but 

 there ought not to be a great difference 

 in this respect between Jjars cemented 

 at the same time. The common thick- 

 ness is little more than half an -inch. It 

 is not advisable that they should be very 

 broad in proportion to the thickness, us 

 this figure is found to produce flaws and 

 cracks in the direction of the length of 

 the bar. The bars may be square, or 

 their breadth may conveniently be some- 

 what more than twice their thickness. 

 The fire for cementation must be of con- 

 siderable intensity, and kept up until the 

 conversion has perfectly taken place, 



