278 -THE SCIENTIFIC PAPERS OF 



higher temperature ; whilst there were certain ores which were 

 not reducible at a temperature below 1500 or 2000 Fahr. 

 Those were the dense magnetic oxides which had no gases to give 

 out, but were perfectly dense, like a piece of glass. Such compact 

 ores, he believed, were not reduced in the upper part of the blast 

 furnace in the way supposed viz., by a current of carbonic acid, 

 but only in a lower part of the furnace after they had become 

 liquid. Certain ores, such as Ilmenite or Marbella ore, had been 

 known to pass through the blast furnace and to come out un- 

 changed with the slag, notwithstanding the heat through which, 

 they had passed. He thought if such pieces of ore could tell a 

 tale, they would speak of actions and reactions going on in the 

 blast furnace which did not altogether tally with the beautiful 

 stratifications Mr. Bell had shown. The author's conclusion, that 

 the hot blast could not be beneficial beyond a certain point, was 

 mainly based upon the argument, that with the temperature of 

 the blast the heat towards the top of the furnace was also in- 

 creased. But the temperature of the blast affected the temperature 

 at the top of the furnace in the contrary way to what Mr. Bell 

 had in his argument supposed. If the temperature of the blast 

 were suddenly raised, then indeed a rise would be perceptible 

 throughout the furnaces, and the gases would escape at a somewhat 

 higher temperature. In that case the same amount of oxygen 

 would be introduced, and the same amount of carbon accompanied 

 the charge ; therefore there must be the same proportion of car- 

 bonic oxide and of carbonic acid issuing at the top, with an increase 

 of temperature resulting from the greater importation of free heat 

 with the blast. But if at the same moment when the temperature 

 of the blast was raised, the relative quantity of coke in the furnace 

 could be diminished, to the point of producing not more than the 

 requisite amount of heat, then a diminished quantity of products 

 of combustion would have to impart its heat to the same quantity 

 of ore ; and inasmuch as the relative quantity of matter to be 

 heated and smelted would be increased, it followed that the 

 temperature of the escaping gases must be less than before, and 

 that there must be advantage in raising the temperature of the 

 blast. 



As to the effect of the increased temperature of the blast upon 

 the temperature of the crucible of the blast furnace, he had 



