210 
iron. 
posed to external air, or to the combustion of fine steel 
filings in a white flame ; if, when issuing from the orifice 
of the furnace, it is of the purest white colour, possessing 
no tenacity, but in a state of the greatest fluid division, 
and, when cold, resembles a mass of heavy torrefied spar, 
void of the smallest vitrid appearance, hard and durable, 
it is then certain that the furnace contains sulphury iron , 
L e. super-carbonated iron. At blast-furnaces, where a 
great quantity of air is thrown in per minute, super-carbo- 
nated crude iron will be obtained with a cinder of a longer 
form, with a rough flinty fracture towards the outside of 
the column. 
That cinder which indicates the presence of carbonated 
iron in the hearth of the furnace, forms itself into circular 
compact streams, which become consolidated and insert- 
ed into each other ; these are in length from three to nine j 
feet. Their colour, when the iron approaches the first 
quality, is a beautiful variegation of white and blue ena- 
mel, forming a wild profusion of the elements of every 
known figure ; the blues are lighter or darker according 
to the quantity of the metal and the action of the external 
air while cooling. When the quality of the pig-iron is 
sparingly carbonated, the blue colour is less vivid, less de- 
licate ; and the external surface rougher, and more sullied 
with a mixture of colour. The same scoria, when fused 
in vessels which are allowed to cool gradually, parts with 
all its variety of light and shade, and becomes of a yellow- 
ish colour, sometimes nearly white when the quantity of 
incorporated metal has been small. 
The cinder which is emitted from the blast-furnace 
•* 
when carbo- oxygenated (or No. 3,) iron is produced, as- 
sumes a long zig-zag form. The stream is slightly con- 
vex in the middle ; broad, flat, and obliquely furrowed 
towards the edges. The end of the stream frequently 
rears itself into narrow tapered cones, to the height of six 
