IRON 1007 



the previously cold regenerator chambers, c, B, to a correspondingly higher heat. After 

 about an hour's work the reversing valves, B 1 , are again reversed, and the air and gas 

 enter the first pair of regenerator chambers, c, E, but which are now very hot, and 

 therefore the air and gas become very hot, and enter the furnace in this state, meeting 

 and entering into combustion, and thus producing a still higher temperature, probably 

 500 higher still, and again heating the second pair of regenerator chambers, c 1 , B 1 , so 

 much higher, which enables them to again heat the air and gas to a still higher 

 degree, when the valves, B 1 , are again reversed. Thus an accumulation of heat and 

 an accession of temperature is obtained, step by step, so to speak, until the furnace is 

 as hot as is required ; for unless cold materials are put in to be heated, and thus 

 abstract heat, the temperature rises as long as the furnace holds together, and the 

 supply of gas and air is continued. The heat is at the same time so thoroughly 

 abstracted from the products of combustion by the regenerators that the chimney flue 

 remains always quite cool. The command of the temperature of the furnace and of 

 the quality of the flame is rendered complete by means of the gas and air regulating 

 valves shown at B \nfig. 1266, and by the chimney damper. These are adjusted to 

 any required extent of opening by the notched rods Q, B, and s, (Jig. 1266) respectively, 

 so that having the power of producing as high a temperature as can be desired, there 

 is also the power of varying it according to the requirements in each case. 



The bed of the furnace D D (fig. 1267), is of the ordinary construction, formed of iron 

 plates, and is provided with water-bridges at the ends, as shown, to protect the 

 ' fettling ' (or oxide of iron used for lining the furnace) from being melted away. The 

 overflow from one of the water-bridges is led into a sheet-iron tank below the bed, and 

 then away. The evaporation from this tank keeps the bottom plates cool and preserves 

 the cinder covering them from melting off, and the steam is carried away by a draught 

 of air entering through two holes, i, i (fig. 1266), below the tap-hole, and passing off 

 by small ventilating shafts K, x (fig. 1268), at the back of the furnace. 



A heating chamber, H (fig. 1267), is arranged at each end of the furnace, in which the 

 charge of pig-iron may be heated to redness before it is introduced into the puddling 

 chamber, D, D. 



The advantages of this furnace for puddling, are that the heat can be raised to an 

 almost unlimited degree ; that the flame can be made at will oxidising, neutral, or 

 reducing, without interfering with the temperature; that indraughts of air and cutting 

 flames are avoided ; and that the gas fuel is free from ashes, dust, and other impurities, 

 which are carried into an ordinary puddling furnace from the grate. In this last 

 respect the new furnace presents the same advantages as puddling with wood. 



The ordinary furnace received charges of 484 Ibs. each, and yielded on an average 

 426 Ibs., representing a loss of 12 per cent., whereas the gas-furnace received charges 

 averaging 424 Ibs., and yielded 413 Ibs., representing a loss of less than 2*6 per cent. 



It is important to observe, moreover, that the gas-furnace turned out eighteen heats 

 in three shifts per 24 hours, instead of only 12 heats per 24 hours, which was the limit 

 of production in the ordinary furnace. 



This rate of working was attained without the employment of any arrangement for 

 heating the pig-iron before charging it into the furnace, the heating chambers at the 

 ends not having been used. The adoption of the plan of heating the metal before- 

 hand, a system already extensively in use both in this country and on the Continent, 

 effects a further saving of 1 to 1 5 minutes in the time required for working each charge, 

 as well as a considerable economy in fuel. 



The quality of the iron produced from the gas-furnace was proved decidedly superior 

 to that from the ordinary furnace, being what is technically called best best in the one, 

 and best in the other case, from the same pig. 



The economy of fuel was greatly in favour of the gas-furnace. The saving of fuel 

 in puddling cannot be less than 40 to 50 per cent, in quantity, while a much cheaper 

 quality may be used. 



The composition of ' fettling ' was, however, greater in the gas-furnace, and the 

 superior yield was naturally attributed by the forge managers to that cause. 



By the use of the water-bridge the amount of ' fettling ' required is reduced to an 

 ordinary proportion, the average quantity of red ore used being 92'6 Ibs. per charge, 

 besides the usual allowance of bull dog, while the yield per charge of 483'3 Ibs. of 

 grey forge pig has been increased to 485 Ibs. of puddled bar. 



Danks's Revolving Puddling Furnace. It appears that experiments were first com- 

 menced by Mr. Samuel Banks in May 1868, in the Cincinnati Railway Works. In 

 1869, the first experiments being successful, other revolving furnaces were set to 

 work, and in 1870 they were generally adopted in those works. In a little time several 

 iron producing companies in America being convinced of the advantages of Danks's 

 process, adopted his revolving furnace for puddling. The following description by 

 Mr. Samuel Banks will fully explain the arrangements of his puddling furnace. 



