in the Manufacture of Cast-Iron. 375 
These three materials—the ore, the fuel, and the flux—were 
put into the furnace, near the top, in a state of mixture. The 
only other material supplied was air, which was driven into the 
furnace by pipes from blowing apparatus, and it en- 
tered the furnace by nozzles, sometimes on two oppo- 
site sides of the furnace, sometimes on three, and 
sometimes, but rarely, on four. The air supplied in 
this manner entered near the bottom of the furnace, 
at about 40 feet from the top; where the solid mate- 
rials were put in. The furnace, in shape, consisted, at 
the middle part, of the frustums of two cones, having 
a horizontal base common to both, and the other and 
smaller ends of each prolonged into cylinders, which 
constituted the top and bottom of the furnace, as may 
be well enough conceived from the sectional sketch 
on the margin. 
The whole of the materials put into the furnace, resolved 
themselves into gaseous products, and into liquid products. The 
gaseous products, escaping invisible at the top, included all the 
carbonaceous matter of the coke, probably in the form of carbo- 
nic acid, except only the small portion of carbon retained by the 
cast-iron. The liquid products were collected in the cylindrical 
reservoir, constituting the bottom of the furnace, and there di- 
vided themselves into two portions, the lower and heavier being 
the melted cast-iron, and the upper and lighter being the melted 
slag, resulting from the action of the fixed portion of the flux 
upon the fixed impurities of the fuel and of the ore. 
II. Thus much being understood in regard to the process of 
making cast-iron, as formerly practised, we are now prepared for 
the statement of Mr Nriison’s improvement. 
This improvement consists essentially in heating the air in 
its passage from the blowing apparatus to the furnace. The 
heating has hitherto been effected by making the air pass 
