248 THE SCIENTIFIC PAPERS 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, 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. 3), below the tap hole, 

 and passing off by small ventilating shafts at the back of the 

 furnace. 



A heating chamber, H, 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, arc that the heat 

 can be raised to an almost unlimited degree ; that the flame can 

 be made at will oxidizing, neutral, or reducing, without interfering 

 with the temperature ; that in-draughts 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 following tables give the working results which were 

 obtained from this furnace, as compared with the results obtained 

 at the same time in an ordinary furnace from the same pig (the 

 ordinary forge mixture) : 



