1920+ On the Produfizon of Caft Iron,” 
the fracture of fuch metal prefents an impure mafs covered 
on both faces with a mixture of oxydated iron, of a blueifhk 
colour, nearly metallic. In fhort, this quality of iron is in-_ 
capable of receiving fuch a degree of fiuidity as to enable us 
to judge whether the convexity of its furface is peculiar to its 
ftate, or is owing to its want of divifion as a fluid, whereby 
the gradual confolidation of the metal is prevented. 
Thefe features fufficiently diftinguifh betwixt the various 
qualities of crude iron after they are obtained from the blaft- — 
furnace: there are, however, criterions not lefs infallible, 
whereby we can prejudge the quality of the metal many 
hours before it is run from the furnace. Thefe are the co- 
Jour and form of the fcoria, the colour of the vitrid cruft 
upon the working bars, and the quantity of carburet which 
is attached to it. The variety of colour and form in the cin- 
der almoft univerfally indicate the quality of the metal on 
the hearth. Hence, from a long courfe of experience, have 
arifen the following denominations: ‘‘ Cinder of fulphury 
iron ;”? “ Cinder of No. 1, No. 2, and No. 3;’’ and ‘ Cin- 
der of ballaft iron.” Although at different works, from local 
circumftances, the fame kind of fcoria may not indicate pre- 
cifely the fame quality of iran, yetthe difference is fo fmalk 
that the following defcription of the various cinders may 
convey a very juft idea of their general appearance. 
When the fcoria is of a whitifh colour and fhort form, - 
branching from the notch of the dam, and emitting from its 
fiream beautiful fparks of ignited carbon, refembling thofé 
ejected from a crucible of caft fteel in fufion, expofed to ex- — 
ternal air, or to the combuftion of fine fteel filings in a white ~ 
flame; if, when iffuing from the orifice of the furnace, it is — 
of the pureft white colour, poffeffing no tenacity, butin a — 
ftate of the greateft fluid divifion, and, when cold, refembles: 
a mafs of heavy torrefied fpar, void of the fmalleft vitridap- — 
pearance, hard and durable, it is then certain that the fur- — 
nace contains /ulibury iron, i. ¢. fuper-carbonated iron. At. 
blaft-furnaces, where a great quantity of air is thrown in pen _ 
minute, fuper-carbonated crude iron will be obtained with a 
cinder of a longer form, with a rough flinty fra€ture to- i 
wards the outfide of the column, . 
: That 
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