VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 58C) 



certain egrees: but when ignited to be white, perfectly pure steel is scarcely 

 malleable, e. It becomes black on its polished surface by being wetted with 

 acids, f. Much thinner and more elastic plates can be made of it by hammering 

 than of iron. g. The specific gravity of steel which has been melted and ham- 

 mered, is in general greater than that of forged iron. h. With the aid of sul- 

 phuric acid it decompounds a smaller quantity of water than an equal weight of 

 forged iron. i. It decompounds water, in the cold, more slowly than forged 

 iron. k. By repeated ignition in a rather open vessel, and by hammering, it 

 becomes wrought or forged iron. 1. It affords a residue of at least ^-i-g- its 

 weight of carbon on dissolution in diluted sulphuric acid. m. It is more sono- 

 rous than forged iron. n. On quenching in cold water, when ignited, it retains 

 about -I of the extension produced by ignition; whereas wrought iron so treated 

 returns to nearly its former magnitude. 



3. By the term crude, or raw iron, I understand that kind of iron which pos- 

 sesses the following properties : a. It is scarcely malleable at any temperature. 

 b. It is commonly so hard as to resist totally, or very considerably, the file. c. It 

 is not susceptible of being hardened or softened, or but in a slight degree, by 

 ignition and cooling, d. It is very brittle, even after it has been attempted to be 

 softened by ignition and cooling gradually, e. It is fusible, in a close vessel, at 

 about 130° of Wedgwood's pyrometer, f. With sulphuric acid it generally de- 

 compounds a smaller quantity of water than an equal weight of steel, g. It de- 

 compounds water in the cold more slowly than wrought iron. h. It unites to 

 oxygen of oxygen gaz as slowly, or more slowly than even steel, i. By solution 

 in sulphuric and other acids, it leaves a residue not only of carbon, but of earth; 

 which exceed the quantity of residue from an equal weight of steel, k. It is 

 perhaps more sonorous than steel. 



With respect to interior structure: 



1. Wrought iron is to be considered as a simple or undecompounded body, 

 but it has not been hitherto manufactured quite free from carbon ; which is to be 

 reckoned an impurity. The least impure iron, as indicated by properties, is 

 that which possesses the greatest softness, toughness, and strength ; but if it be 

 soft, independent of combination, it will of course be of the toughest and strongest 

 quality. To denominate it from properties, I would call it soft malleable iron : 

 and from internal structure, it should be called pure iron, or iron. The ore 

 from the deep mines of Dannemora, produces the purest iron. It is in England 

 called Oeregrund iron.* It is almost the only iron manufactured which by 

 cementation afFonls what our artists reckon good steel. 



* Oeregrund is not the name of the country in which the ore of this iron is gotten j or of the place 

 where it is manufactured ; but it is the name of a sea-port town, from which the iron of Dannemora 

 was formerly exported. — Orig. 



