SIR WILLIAM SIEMENS, F.R.S. 257 



that even if it were a perfect conductor of heat and presented an 

 unlimited extent of surface for absorbing the heat from the gas, 

 thnv would still be a certain amount of heat that would escape at 

 the furnace top ; and in increasing the height of the furnace, a 

 neutral point would speedily be reached, beyond which no further 

 increase of height would produce any further absorption of heat, 

 for the reason that the quantity of ore charged could not on the 

 average exceed the quantity of ore smelted during the same 

 interval of time, and its relative capacity for heat could not be 

 increased by an augmentation of heat-absorbing surface. The 

 saving consequent upon increased capacity of the blast furnace 

 would continue to increase until a certain minimum consumption 

 of fuel was reached, but this would not be the theoretical minimum 

 assigned by chemical calculations. The ore could not do more 

 than take up a certain amount of heat from the gas ; and sup- 

 posing that its capacity for heat were sufficient to reduce the 

 temperature of the gas down to 500 or 400, that would be the 

 temperature at which the gas must then escape ; and no further 

 saving would be possible. If the relative quantity of ore that 

 could be charged into the furnace were indefinitely great, then 

 indeed the escaping gas could be cooled down as low as the 

 temperature of the external atmosphere ; but inasmuch as the 

 quantity of ore charged into the furnace top was the same as the 

 quantity smelted in the lower part of the furnace, this ore could 

 not absorb more than a certain maximum quantity of heat, and 

 all the surplus heat in the waste gas must escape. There was also 

 the further question whether with anything like such a small 

 proportion of coke a sufficient temperature could be obtained in 

 the furnace to ensure the perfect fusion of the ore : for this pur- 

 pose an infinitely high temperature of blast would be requisite, 

 but with a blast at only 1000 temperature it would certainly be 

 impossible to attain to anything like the theoretical minimum 

 consumption, which left no margin at all of extra carbon for pro- 

 ducing the heat required for smelting the ore ; and it must be 

 borne in mind that the mere transfer of oxygen from the ore to 

 the carbon was not attended by any evolution of heat, but by an 

 absolute absorption of heat. 



Mr. C. W. Siemens did not understand how the temperature of 

 VOL. i. s 



