IRON 



945 



and over, presenting continually new surfaces to the heated lining and to the flame 

 within the rotator. 



During the time of this reaction, carbonic oxide gas is evolved from the mixture of 

 ore and carbon, and heated air only is introduced from the regenerator, to effect its 

 combustion within the rotating chamber. The gas from the gas-producers is entirely, 

 or almost entirely, shut off during this portion of the process. When the reduction of 

 the iron ore is thus nearly completed, the rotator is stopped in the proper position for 

 tapping off the fluid cinder; after this the quick speed is imparted to the rotator, 

 whereby the loose masses of iron contained in it are rapidly collected into two or three 

 metallic balls. These are taken out and shingled in the usual way of consolidating 

 puddled balls ; the furnace is tapped again, and is ready to receive another charge of 

 ore. The time occupied in working one charge rarely exceeds two hours : and sup- 

 posing that 10 cwts. of metallic iron is got out per charge, the apparatus is capable of 

 turning out at least 5 tons of puddled bar per diem. If anthracite or hard coke is 

 available for effecting the reduction of the ore, it should be crushed much finer than 

 when coal or brown coal is used, the idea being that each particle of the reducing agent 

 should be consumed during the period of chemical reduction. If wood is used, it must 

 be charged, for the same reason, in still larger pieces. 



It is feasible to push the operation within the rotator to the point of obtaining cast 

 steel. If this is intended, the relative amount of carbonaceous matter is somewhat 

 increased in the first instance, so that the ball if shingled, would be of the nature of 

 puddled steel, or contain even more carbon mechanically enclosed. 



It may however be asked, why the rotating furnace should admit of the complete 

 combustion of carbon, whereas in the blast-furnace such complete combustion is, as is 

 well known, not possible, because each atom of carbonic acid formed would immediately 

 split up into two atoms of carbonic oxide by taking up another equivalent of carbon 

 from the coke present ? The following explanation will serve to elucidate this point : 

 In the rotative furnace streams of carbonic oxide are set up within the mass under 

 reaction, and this carbonic oxide on reaching the surface meets the current of intensely- 



" heated air proceeding from the regenerators, and completes with its perfect combustion 

 within the free space of the chamber. The carbonic acid thus generated comes in no 

 further contact with the carbon, consequently it cannot split up, but is drawn away 



unchanged into the chimney, while the evolved heat is taken up by the sides of the 



chamber, and transmitted by reverberation and conduction to the mixture of ore, fluxes, 



and coal. 



Charcoal Blast-Furnace. The 



general form of the charcoal blast- 

 furnace, as used in the United 



States, where this fuel is com- 

 mon, is shown in vertical section 



in fig. 1219, and in section 



through the tuyere arches in 



fig. 1218. The ores designed to 



be smelted in this furnace are 



hydrated oxides of iron, such 



as brown haematite, brown iron- 

 stone, pipe-ore, and bog-ores. 



The height is 35 feet; hearth 



from base to the boshes, 5 feet 6 



inches ; width at the bottom, 24 



inches ; and at top, 36 inches. 



The tuyeres are 20 inches 



above the base. The boshes are 



9 feet 6 inches in diameter, and 



measure from the top of the 



crucible 4 feet, which gives about 



60 slope. The blast is con- 

 ducted through sheet-iron or 



cast-iron pipes laid below the 



bottom stone into the tuyeres. 



The top is furnished with a 



chimney, by which the blaze from 



the tunnel head is drawn off. 



Around the top is a fence of iron 



or wood. Fig. 1220 shows the 



method of preparing and arranging the hearthstones, d is the bottom stone, made 



of a fine close-grained sandstone, from 12 to 15 inches thick, at least 4 feet wide, and 

 VOL. II. 3 P 



1218 



