112 | / Observations on Fron and Steel. 
thousand to twelve hundred square feet in a minute. 
The air passes through a pipe, the diameter of which 
is from two inches and a quarter, to two and three 
quarters, wide. The compression of air which is 
necessary is equal to a column of water four feet 
and half high. The ore melts as it passes through 
the fire and is collected at the bottom, where it is 
maintained in a liquid state. The slagg, which falls 
down with the fused metal, is let off, by means of an 
opening in the side of the furnace, at the discretion 
of the workmen.” 
When a sufficient quantity of regulus, or imper- 
fectly reduced metal, is accumulated at the bottom 
of the furnace (which usually happens every eight 
hour's), it is let off into moulds; to form it for the 
“purposes intended, such as cannon or pig iron. 
Crude iron is distinguished into white, black, and 
grey. The white is the least reduced, and more 
brittle than the other two. The black is that with’ 
which a large quantity of fuel has been used; and 
_the grey is that which has been reduced with a suffi- 
cient quantity of fuel, of which it contains a part in 
. solution. ; 
The operation of refining crude iron consists in. 
burning the combustible matter which it holds in so- 
lution; at the same time that the remaining iron’ is 
more perfectly reduced, and acquires a fibrous tex- 
ture. For this purpose, the pigs of cast iron are 
taken to the forge; where they are first put into what 
‘ 
