On the Blast Furnace in the Manufacturé of Iron. 101 
is first converted into carbonic acid, and then, if the bed of coal 
be thick enough, this last will be changed into carbonic oxide. 
As this however is generally not the case, a part of the carbonic 
acid passes beyond the upper surface of the fuel without having 
undergone a change, particularly if the blast from below has been 
strong and abundant. By this operation the chamber B becomes 
- heated, and a mixture of carbonic acid, carbonic oxide, nitrogen, 
and a little hydrogen passed out ofthe flue C. The object of 
the metallurgist, however, is not to permit any carbonic oxide or 
hydrogen to escape combustion, but to endeavor to add to the 
heat of the furnace, that heat arising from the combustion of these 
two gases. This is readily accomplished by throwing in a sec- 
ond blast of air, through a number of small orifices just above 
the surface of the fuel, D; this blast to be regulated as required. 
By this process we re-create, as it were, the maximum intensi- 
ty of heat (which first shows itself at the lower part of the fuel 
on the grate, just where the air becomes converted into carbonic 
acid, ) and in the chamber B, where it is most wanted ; for the 
amount of heat rendered latent by the reduction of the carbonic 
acid into carbonic oxide, is rendered sensible by the reproduction 
of the former. 
~The advantages arising from this method of burning the fuel, 
are important. In the first place, the heat is diffused over a lar- 
ger space, thereby heating more uniformly the metal, than when 
it is placed in the midst of the fuel. Again, fuel of the most in- 
ferior quality can be made use of, and as evidence of this in some 
trials made at Audincourt, it was proved that the reverberatory 
furnace could be heated to whiteness by burning the gas, and the 
pig melted and puddled, when a mixture of charcoal dust and 
earthy matter was made use of as fuel. - 
Kbelman, whom I have so often quoted in these articles, and 
who has certainly made the best series of scientific researches 
upon the subject, says that instead of employing the action of air 
upon an excess of charcoal to produce the combustible gas, the 
vapor of water may to an extent be substituted, which produces, 
in contact with burning charcoal, carbonic oxide and hydrogen. 
The heat of the combustion of equal volumes of hydrogen and 
carbonic oxide is about the same, and it can be easily deduced 
that the decomposition of the vapor of water by the charcoal, de- 
termines an absorption of latent heat, equal to that which is pro- 
