and the Operations of the Blafl-Furnace. I 33 
That cinder which indicates the prefence of carbonated 
iron in the hearth of the furnace, forms itfelf into circular 
compact fireams, which become confolidated and inferted 
into each other; thefe are in length from three to nine feet. 
Their colour, when the iron approaches the firft quality, is a 
beautiful variegation of white and blue enamel, forming a 
wild profufion of the elements of every known figure; the 
blues are lighter or darker according to the quanuty of the 
metal and the aétion of the external air while cooling. When 
the quality of the pig-iron is fparingly carbonated, the blue 
colour is lefs vivid, Jefs delicate; and the externa] furface 
rougher, and more fullied with a mixture of colour. The 
fame feoria, when fufed in vefiels which are allowed to cool 
gradually, parts with all-its variety of light and fhade, and 
becomes of a yellowifh colour, fometimes nearly white when 
the quantity of incorporated metal has been {mall.. 
The cinder which is emitted from the bla{t-furnace when 
carbo-oxygenated (or No. 3,) iren is produced, affumes a 
long zig-zag form. The ftream is flightly convex in the 
middle; broad, flat, and obliquely furrowed towards the 
edges. The end of the ftreani frequently. rears itfelf into 
narrow tapered cones, to the height of fix or eight inches: 
thefe are generally hollow in the centre, and are eafily de- 
molifhed, owing to their exceflive brittlenefs. The colour 
of this lava is very various; for the moft part it is pale yel- 
low mixed with green, Its tenacity is fo great, that if, while 
fluid, a fmall iron hook is inferted into it at a certain degree 
of heat, and then drawn from it” with a quick but fteady 
‘motion, 20 to 30 yards of fine glafs thread may be formed 
with eafe. If the colours are vivid and variegated, the thread 
wil] poffefs, upon a minute feale, all the various tints of co- 
louring which is found in the columnar mafs. , When by 
accident a quantity of this lava runs back upon the difcharg~ 
ing-pipe, it is upon the return of the blafL impelled with fuch 
velocity as to be blown into minute delicate fibres, fmaller 
than the moft ductile wire; at firft they float upon the air 
like wool, and when at reft very much refemble that fub- 
flance. 
The prefence of oxygenated crude iron (Na. 4,) on the 
furnace~ 
A 
