On the Principles of Tron and Steel. 167 
the very wide difference betwixt crude iron and caft ftecl 
when applied to ufe. 
- This amongft many other pofitions might be adduced to 
prove that carbon exifts united in a gafeous ftate to iron, and 
conftitutes fteel ; or, in other words, that iron to cenftitute 
fteel muft hold in folution a portion of carbon, not lefs than 
z+sth part of its own weight. 
Some of the foreign writers account for the difference be- 
twixt fteel and crude iron, by affirming that the former is 
iron perfecily reduced to which carbon is given, and that the 
jatter is only iron imperfectly reduced, and which alfo con- 
tains carbon. ‘This is a feeble diftinétion. Iron knows of 
no ftate of imperfe& exiftence as a metal; the particles of 
iron ina crude ftate are equally difpofed to become mal- 
Jeable, fo foon as the carben which has interpofed itfelf be- 
twixt them is burnt out. The fame operation muft take 
place before fteel is brought back to the ftate of malleable 
iron; hence, according to the reafoning of the French writ- 
ers, they are both imperfect ftates ef the metal. 
Crude iron is only fo far imperfeét, becaufe it contains 
carbon in a material ftate. Steel may be faid to be more 
perfect, becaufe it is united to carbon in an elaflic fiate; 
and iron, properly fe called, is perfe& in proportion as it is 
void of thefe impurities. 
‘Steel alfo poffeffes the fole property of acquiring a degree 
of hardnefs, when immerfed at certain degrees of heat into 
cold water, which enables it to perforate and aé upon all 
other metallic fubftances. This is occafioned by the fudden 
expulfion of the caloric from the interftices of the metal, 
which brings on an inftantancous ageregation of the particles, 
and which renders the frature uncommonly clofe and re- 
gular. Expofure toa fimilar degree of heat, and cooling in 
the open air, brings it back to its ufual ftate, capable of being 
again and again hardened, and not to the ftate of malleable 
jren, as a late effayift on iron has erroneoufly fated. 
M4 Having 
