Obfervatiom en Iron and Steel. 5* 



tollers, that the iron is deprived of the remaining portion of 

 impurity, and acquires a fibrous texture. 



The iron made by the three foregoing procefles is equally 

 Valuable, for by any of them the metal is rendered pure ; but 

 after thofe different operations are finifhed, it is the opinion 

 of many of the mod judicious workers in iron, that laying 

 it in a damp place for fome time improves its quality ; and 

 to this alone fome attribute the fuperiority of foreign iron, 

 more time elapfing between making and ufing the metal. 

 To the latter part of this opinion I can by no means accede, 

 as it is well known that the Swedifh * ores contain much 

 lefs heterogeneous matter than ours, and are generally 

 much richer* as they ufually yield about -jo per quintal of 

 pure iron, whereas the average of ours is. net more than 

 30 or 40 f: add to this, that the Swedifh ores are fmelted 

 in wood fires, which gives the iron an additional fuperiority. 



Iron inftruments are cafe-hardened by heating them in a 

 cinder or charcoal fire ; but if the firft be ufed, a quantity of 

 old leather or bones muft be burnt in the fire, to fupply the 

 metal with carbon. The fire muft be urged by a pair of 

 bellows to a fufficient degree of heat, and the whole opera- 

 tion is ufually completed in an hour. 



The procefs for cafe-hardening iron is in fact the fame as 

 for converting iron into fteel, but not continued fo long, as 

 the furface only of the article is to be impregnated with car- 

 bon. Some attempts have been made to give caft-iron, by 

 cafe-hardening, the texture and du&ility of fteel ; but they 

 have not been very fuccefsful. Table and pen-knife blades 

 have been made of it •, and, when ground, have had a pretty 

 good appearance •, but the edges are not firm, and they foon 

 lofe their polifh. Common table knives are frequently made 

 of this metal. The cementation of iron converts it into 



* Steel is commonly made of Swedifh iron. 



f The iron made from the ore found in the neighbourhood of Sheffield 

 domains a great deal of phofphate of iron or fiderite, which renders the 



metal brittle when cold. 



E 2 fteel, 



