& On Ibe different "Proportions of Carbon, &e. 



metallic button of crude iron below; it is with the greater! 

 difficulty we can admit of the prefence of oxygen in the me- 

 tallic mafs. It may be urged, that charcoal, confidered as 

 an oxide of carbon, might impart a portion of oxygen to the 

 metal. This muft fuppofe, however, a continual action and 

 reaction of affinity, wherein it is prefumable the carbon 

 would finally prevail, and carry off the oxygen. I conceive 

 it more iuft to fuppofe, that what quantity of oxygen was 

 contained in the charcoal, would be difcharged by the latter 

 deoxydating itfelf analogous to its fuperior affinity, rather 

 than combining with the iron. 



It is a fact well known amongft manufacturers, that caft 

 iron of a filvery white fracture may be faturated toexcefs with 

 carbonaceous matter (imply by cementing it in contact with 

 charcoal. In this procefs it acquires a foft gray fracture, 

 eaflly reducible by the file. If this caft iron originally con- 

 tained oxygen, a long cementation in contact with charcoal, 

 moft likely, would deprive it of this ; yet we find it ftill pof- 

 feffed of all the properties of caft iron. From this we fhould 

 be apt to conclude that oxygen at leaft is not neceffary to 

 the production of crude iron. 



Again, in the procefs of cementation bar iron is firft 

 changed, by a comparatively fmall dofe of carbon, into fteel. 

 If this fteel, by accident or intention, be continued fome- 

 what longer in the furnace under an increafed temperature, 

 an excefs of affinity is eftablifhed betwixt the metal and the 

 charcoal without the prefence of a third principle : the fteel 

 becomes gradually more and more carbonated : it changes 

 its fracture of granulation, if I may be allowed the term, 

 from that peculiar to bliftered fteel, through all thofe breaks 

 peculiar to the refpective qualities of crude iron ; and may 

 at laft pafs into the ftate of a carburet of iron totally different 

 in its properties and appearance from either fleel or crude 

 iron. This procefs may be carried on to the utter exclufion 

 of atmofpheric air; and here, if the procefs is flopped in its 

 proper ftages, will be found all the various qualities of crude 

 iron formed without perfect fufion, where we cannot con- 

 ceive oxygen to have exifted. 



I am aware of adducing circumftanccs from thefe experi- 

 ments, at variance with the prefent received opinions upon 

 the conftitient parts of caft iron, and alfo in oppofition to 

 principles which I have formerly laid down. I wifh not the 

 prefent hints to be confidered as affertions. As irreconcile- 

 able in fome degree with former opinions, I wifh they may 

 lead to an ample inveftigation of the fubject. The diffiiu - 

 tion hitherto made betwixt crude iron and fteel. particularly 



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