On the Component Parts of Iron-jlones. 307 



fulphur. Some contend that fulphur is eafily difplaced, and 

 that therefore the iron-Hone fhoulcl be moderately calcined', 

 left the fulphur from the coal ufed in burning it fhould 

 enter, and again hurt the quality of the iron. On the other 

 hand, it is faid that fulphur is of difficult expulfion from the 

 centre of the ftone, as it is never leen going off till a bright 

 red heat forcibly expels it; and therefore it is highly re- 

 quisite the iron-ftone fhould be long and violently expofed 

 till the laft portion is got rid of. To effect this, therefore, 

 the heat, fay they, ought to be urged till fuch time as the 

 ftone has indicated figns of fufion, or has partially fuffered 

 thereby. In order to give ftrength to this opinion, thofe 

 who adopt it add, that, by fuch fevere calcination, the 

 volume of ftone is reduced, becomes heavier, and that it will 

 confequently occupy lefs room in the blaft-furnace j of 

 courfe it is imagined that, bulk for bulk, the iron-ftone 

 becomes richer in iron than when in a raw ftate. 



Thofe who are acquainted with the oxydation of metals, 

 and the confequent increafe of weight, will at once difcove? 

 the fource of this error, and readily conceive, that, after the 

 metal in the iron-ftone has become partially difengaged by 

 the expulfion of water, carbon acid, fulphur, 8cc. forming 

 frequently a third part of the whole weight, it will become 

 an object of attack to the oxygen of the atmofpheric air j 

 the combination of which with the iron alone adds to the 

 actual increafe of weight, and not the tranfpofition of the 

 partieles of metal from one piece of iron-ftone to another. 

 It muft alfo be obvious that, where fuch fallacious pre- 

 judices have taken root, the confequences muft frequently 

 he fatal to the interefts of the manufacturer ; as fuch iron- 

 , literally calcined, muft require an additional portion 

 of fuel to furnifl) carbon to carry off the fuperadded oxygen. 



It is fomewhat rcmaikahle that the phenomena attending 



»-:ydation of iron fhould be entirely unknown at iron 



Dianufa&ories. Such a procefs is never dreamt of, and 



even the declauners agaiuft fevere torrefa&ion only account 



for 

 5 



