Iron* 
15$ 
foraily preferred for tough and heavy work. Hence, this 
last or Jorge pig, is carbonated iron, wherein the cliarco A 
lias nearly abstracted the whole of the oxygen : smooth 
faced pig is carburetted iron, where the charcoal has su- 
perabundantly combined with the iron : the white and 
the mottled iron, is imperfectly and irregularly carbona- 
ted, and is least valuable. 
The other parts of the furnace, are, from the boshes to 
the entrance of the blast, in which is to be considered whe- 
ther the width and slope, will admit of the required regu- 
lar descent— from the bottom of the boshes to the entrance 
of the blast where the iron and slag is finally fused ; con- 
cerning which the points of consideration are the quantity, 
the velocity, and the direction of the blast— and the hearth, 
in which the melted metal is deposited. 
1 Sthly, In addition to the observations as to the pro- 
portions of charge, I would observe that in England, a 
common charge by weight, is four of coak, three and one- 
third argillaceous iron ore, and one limestone. At a fur- 
nace in England producing good melting iron, of a quali- 
ty between the highly carburetted dark grey iron. No. I, 
and the imperfectly white iron or forge pig carbonated- 
working an argillaceous iron ore containing 27 per cent, 
of iron— the furnace being 45 feet high, and twelve and 
a half feet diameter at the widest part— consuming 2500 
cubic feet of air per minute, issuing from a tuyere of two 
and three fourth inches— the average charges of coak per 
shift (or 12 hours) are fifty of two and three-fourths hun- 
dred weight each, or nearly seven tons. The calcined or 
roasted ore for good melting iron, is of the same quantity, 
but for forge pig, or the least carbonated variety, 6 of coak 
to 7 of ore : the .unburnt limestone is as 4 to 11 of ore. 
This furnace with such a daily charge produces 40 tons 
of metal per week. 
A wood charcoal furnace requires somewhat less lime 
U 
