232 THE SCIENTIFIC PAPERS OF 



the regenerators, are a positive gain to the heat of the furnace, 

 because, having been in contact with comparatively cold metal, 

 they would be at a heat inferior to that of the upper portions of 

 the regenerators, and would therefore only lower their tempera- 

 tures. 



As the bars sink in the hoppers by their gravity, they are 

 followed up by additional bars until the metal charged amounts to 

 about three tons, all of which will be rendered fluid within about 

 four hours from the time of commencing the charge. The metallic 

 bath is tested from time to time by the introduction of a bar 

 through one of the front doors of the furnace, and if the bath 

 should become thick before the end of the operation, although the 

 heat has been maintained, it will be necessary to introduce an 

 additional quantity of pig-metal. All the metal being liquid, a 

 sample is taken out by means of a small iron ladle, and plunged 

 into cold water while still red-hot. In breaking this sample upon 

 an anvil, the temper and quality of the metal may be fairly judged. 

 Its fracture should be bright and crystalline, betokening a 

 very small proportion of carbon (not exceeding '1 per cent.), 

 and the metal should be tough and malleable, notwithstanding 

 its sudden refrigeration. From 5 to 8 per cent, of Spiegeleisen 

 (containing not less than 9 per cent, of manganese) is there- 

 upon charged through the side openings upon the bank of the 

 furnace, and allowed to melt down into the bath, which is 

 then stirred and made ready for tapping in the manner before 

 described. 



The amount of carbon introduced with the Spiegeleisen deter- 

 mines the temper of the steel produced, the manganese being 

 necessary to prevent redshortness, unless Swedish or Styrian iron 

 is used. 



When old iron rails or scrap of inferior quality are charged, the 

 addition of manganese does not suffice to effect the necessary 

 purification of the steel produced ; but the perfectly liquid con- 

 dition of the bath, together with the unlimited time available for 

 chemical reaction, offer extraordinary advantages for the introduc- 

 tion of such materials as may be found to combine with sulphur, 

 phosphorus, silicon, or arsenic, which are the usual antagonists 

 to be dealt with. 



The experiments which I have been able to institute in this 



