WILLIAM SIEMENS, F.R.S. 259 



arrived at as to the quantity of coke that should be sufficient for 

 smelting a ton of iron in a blast furnace having a capacity carried 

 to the ultimate limits then indicated. The 7i cwts. of coke per 

 ton of iron, which had been originally named as the theoretical 

 minimum consumption, represented no more than the carbon 

 necessary for combining chemically with the peroxide of iron or 

 i ah- i ued ore, and for carbonising the reduced metal so as to bring 

 it into the state of ordinary pig iron ; and the idea that it would 

 be theoretically possible, by any increase in the capacity of the 

 blast furnace, to bring down the consumption of coke to that 

 amount, arose from the error of taking a simple arithmetical 

 progression to represent the saving of coke consequent upon 

 successive additions to the size of the furnace. In the supple- 

 mentary paper now read however, an amended calculation had 

 been offered, by taking into account the reduced capital, that is 

 the reduced quantity of coke in the larger furnaces, upon which 

 the percentage of saving had to be estimated ; so that the same 

 percentage of saving, out of a total consumption which was 

 diminished by each successive addition to the capacity of the 

 furnace, represented a less and less absolute saving as the size of 

 the furnace was increased. In this way, considering only the 

 question of abstracting the heat from the escaping gas, the result 

 now arrived at had been that 17'9 cwts. of coke per ton of iron 

 was the limit of minimum consumption that could be attained by 

 simply adding to the height of the furnace, ftb account however 

 had been taken of the chemical work that had to be constantly 

 performed within the blast furnace ; and moreover the additional 

 quantity of heat that could be taken up from the gas by merely 

 adding more material in the furnace top would be found, he 

 considered, to be a very small amount. For although he had 

 shown that, by means of the regenerative system, with a quantity 

 of cooling material relatively very much smaller than was con- 

 tained in a blast-furnace top, it was quite practicable to take up 

 the heat from the outgoing current down to within 20 or 30 of 

 the incoming draught, yet this was only the case so long as the 

 two opposite currents were equal in the amount of their total 

 capacity for heat ; but if the current passing in one direction 

 through the regenerator had a different total capacity for heat 

 from that passing in the opposite direction, then whatever extent 



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