130 On the Produéction of Caft Iron, 
indeed it feems a principle in all metallic fluids, that they 
are convex in proportion to, the quantity of carbon with which 
thev are faturated. ‘This iron flows dead and ponderous, and 
rarely parts in fhades but at the diftance of fome inches from 
each other, 
This is a flight fketch of the appearance of the two ex- 
treme qualities of crude, or pig-iron, when in a ftate of fu- 
fion. According to the divifion formerly made, there ftill 
remains two intermediate ftages of quality to be deferibed : 
thefe are, carbonated and carbo-oxygenated iron; that is, 
No. 2 andg of the manufacturers. Carbonated iron exhi- 
bits, like No. 1, a beautiful appearance in the runner and 
pig. ‘The breakings of the fluid, in general, are lefs fine s 
the agitation lefs delicate ; though the em of the fluid is 
equal, if not beyond that of the other. When the internal 
ebullition of the metal is greate(t, the undulating fhades are 
fmalleft and moft numerous: fometimes they affume the 
fhape of {mall fegments; fometimes fibrated groups; and at 
other times minute circles, of a mellower colour than the 
eround of the fluid. The furface of this metal, expofed to 
external air, when cooling is generally flightly convex, and 
full of punétures: thefe, intron of a weak and fufible nature, 
are commonly finall in the diameter, and of no great depth. 
In firong metal, the punctures are much wider and deeper. 
This criterion, however, is not infallible, when pig-iron of 
different, works is taken collectively. At each individual 
work, however, that iron will be ftrongeft whofe honey- 
combs are largeft and deepett. 
Carbo-oxygenated, or No. 3, pig-iron, runs f{moothly, 
without any great degree of ebullition or difengagement of 
metallic {parks. The partings upon its furface are longer, 
and at greater diftances from each other than in the former 
varieties ; the fhape they affume is either elliptical, circular, 
or curved. In cooling, this metal acquires a confidezable por- 
tion of oxyde; the furface is neither markedly convex nor — 
concave; the punctures are lefs, and frequently vanifh alto- 
gether. Their ablence, however, is no token of a fmooth — 
face fueceeding: in qualities of crude iron oxygenated be- 
yond this, 1 have already mentioned that a concaye furface 
Ss 
aie oa 
—_— 
—_— ee ee 
—_— ee ee eee 
