in the Manufacture of Cast-iron. S75 



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 Neilson'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 



