370 
Cast Steel. 
crude iron. If it be admitted that bar iron is destitute of 
oxygen, which it is highly probable is the case ; if a por- 
tion of this iron be introduced and fused along with a por- 
tion of carbonaceous matter in a vessel impervious to air, 
which vessel is found, when cold, to be more than half 
filled with charcoal, protecting a metallic button of crude 
iron below ; it. is with the greatest difficulty we can ad- 
mit of the presence of oxygen in the metallic mass. It 
may be urged, that charcoal, considered as an oxyd of car- 
bon, might impart a partion of oxygen to the metal. This 
must suppose, however, a continual action and reaction 
of affinity, wherein it is presumable the carbon would final- 
ly prevail, and carry off the oxygen. I conceive it more 
just to suppose, that what quantity of oxygen was con- 
tained in the charcoal, would be discharged by the latter 
deoxydating itself analogous to its superior affinity, rather 
than combining with the iron. 
It is a fact well known amongst manufacturers, that 
cast iron of a silvery white fracture may be saturated to ex- 
cess with carbonaceous matter simply by cementing it in 
contact with charcoal. In this process it acquires a soft 
grey fracture, easily reducible by the file. If this cast iron 
originally contained oxygen, a long cementation in con- 
tact with charcoal, most likely, would deprive it of this ; 
yet we find it still possessed of all the properties of cast 
iron. From this w T e should be apt to conclude that oxygen 
at least is not necessary to the production of crude iron. 
Again, in the process of cementation, bar iron is first 
changed, by a comparatively small dose of carbon, into 
steel. If this steel, by accident or intention, be continued 
somewhat longer in the furnace under an increased tempe- 
rature, an excess of affinity is established betwixt the me- 
tal and the charcoal without the presence of a third prin- 
ciple : the steel becomes gradually more and more carbo- 
nated : it changes its fracture of granulation* if I may be 
