On the Blast Furnace in the Manufacture of Iron. 171 
ble iron, and much therefore depends upon the state in which the 
pig metal passes from this furnace, whether subsequent operations 
will furnish an iron of the first quality or not. The interior of 
the blast furnace consists of three conical cavities, represented by 
the figure. 
A, mouth of the furnace.  __ ey Piles Gis 
AB, fire-room : 
BC, boshes © 
CD, hearth « 
EE, openings called tuyers. 
The principal parts of the furnace are 
thus hastily alluded to, so that those not 
familiar with their names may readily un-  ” 
derstand what follows. In putting the 
blast furnace into operation, the first step 
is to heat it for some time with coal only. 
After the furnace * alate at a proper 
temperature, ore, fuel and flux are thrown 
in alternately, in small quantities, so as to 
have the three ingredients properly mixed 
in their descent. In from twenty five to 
forty eight hours from the time when the 
ore is first thrown in, the entire capacity 
of the furnace, from the tuyer to the mouth, 
- 1s occupied with the ore, fuel and flux, in 
their various stages of transformation. 
~ In order to explain clearly, and in as short a space as possible, 
what these transformations are, and how they are brought about, 
Wwe may consider— 
1. The changes that take place in the descending mass, com- 
posed of ore, fuel and flux. 
2. The changes that take place in the ascending mass, com- 
posed of air and its hygrometric moisture, thrown in at the tuyer. 
3. ‘The Satie action going on hetwoakl the ascending and 
descending masse 
4. The Gaienitha of the gases in various parts of the furnace 
during its operation. 
5. 'The causes that render necessary the great heat of the blast 
furnace. 
