166 On the Principles of Iron-and Steel. 
Tf malleable iron was entirely freed from carbon in the 
manufacturing, the inference would be juft, to ftate that the 
Weight gained was the exact meafure of carbon neceffary 
to form fteel; but as fome malleable irons afford a confider- 
able portion of carbon, it is evident that the total meafure 
of carbon will depend upon the pre-exifting quantity con- 
tained in the iron. The greater the quantityintroduced the 
more brittle will the quality of the fteel be found, and the 
léfs capable of preferving its nature and a folid form, when 
expofed to intenfe degrees of heat. 
Steel, at certain degrees of heat, poffeffes all the foftnefs 
and malleability of iron; but, when cold, partakes of the 
eager brittlenefs of crude iron. When properly hammered, 
if gains fibre, and then becomes the moft elaftic ftate of the 
metal. It is alfo capable of fufion at a high degree of heat : 
it may then be run liquid into iron moulds, and afterwards 
beat out into the moft folid thapes, poffefling cohefion and 
clofenefs of grain, with an aftonifhing degree of flexibility 
and tenacity... In this ftate it is called caft fteel, and is ufed 
for fine inftruments, where durability, polifh and edge are 
requifite. 
In fo far therefore as. fteel is capable of fufion, without 
deftroying its nature; and as it contains iron and carbon 
alone, it muft be confidered as a variety of crude iron free of 
oxygen, and fo far is partially malleable, The fufion of fteek 
deftroys its_property of being welded. This change of nature 
is ocoafioned by the addition of oxygen in the caft fteel fur- 
nace: hence we find, that fufion is incompatible with an 
extreme degree of malleability. 
Since a fmall portion of oxygen is added in the fabrication 
of caft ficel, the component parts of this modification of the 
metal will be, iron, carbon, and a fmall portion of oxygen. 
Admitting then for a moment that the carbon is in the fame 
ftate as in crude iron, here then exifts a fimilarity of prin- 
ciples with carbonated iron, Yet there are few but know 
the 
