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Ox the Principles of Iron and Steel. . 
the great compreffion of air ufed to excite the degree of heat 
neceflary for reduétion. 
Thefe are the foreign fubftances which alter and contami- 
nate the quality of the iron; but, as they exift in different 
proportions in various irons, it is obvious that thefe altera- 
tions of proportion will form varieties of crude iron: the 
following are diftinguifhable : 
1ft. Oxygenated crude iron, where a {mall portion of car- 
bone is united to the iron, and where a fuperabundance of 
oxygen exifts. The fracture of fuch iron prefents a white 
furface deftitute of grain, frequently diverging in ftreaks, re- 
fembling an early variety of cryftallization; fometimes it is 
mottled with fpecks of a black colour, which plainly exhibit 
the feanty portion of carbonic concretions. The external 
furface of fuch iron always cools concave, rough, and co- 
vered with oxyd. In commerce this variety of iron is 
known by the names of white iron, forge pigs, ballaft iron, 
&c. and its prefent yalue is from 5].\5s. to 5l..1§s. per ton. 
ad. Carbo-oxygenated crude iron*, or iron united with 
equal portions of carbon and oxygen. The fraéture of this 
iron is light grey, prefenting a fmall diftin@ grain ; the fur- 
face of the pig partially punétured, lefs concave, and more 
free from oxydation in cooling than the former ftate. In 
commerce it is known by the names of grey iron, No. 3, 
* I am fully aware of the novelty of this term, and that by feme zt 
may be liable to be cenfured. I have, however, the great Lavoifier for 
' my precedent, who, in naming the compound radicals of the vegetable 
kingdom, ufed hydro-carbenous and hydro-carbonic, to exprefs the 
ternary combination of hydrogen and carbon with oxygen; in the 
former, into that of an oxyd—in the latter, into that of an acid. It 
may however be remarked, that in this way the prevailing fubftance 
was marked by a precedency given to its fign, which implied that there 
exitted 2 larger proportion of this than the following fubftance. Let 
the prefent, however, exprefs the combination of iron with carbon and 
oxygen in equal portions: the precedency given to carbon in begin- 
ning the compound, is meant to denote its fuperior agency, and its pre- 
fence being effential in the manufaébure of crude iron, 
&c, 
