258 THE SCIENTIFIC PAPERS OF 



the escaping gas could be independent of the rate of driving of 

 the furnace, unless an excess of heat-absorbing surface had been 

 provided ; because with a greater rate of driving, a given extent 

 of surface would then be called upon to absorb a greater quantity 

 of heat in the same time. When the extent of cooling surface of 

 the materials was so proportioned as to reduce the temperature of 

 the escaping gas to a certain degree, short of the ultimate attain- 

 able point, only a small further quantity of waste heat would be 

 absorbed by passing a greater quantity of gas over the same 

 amount of surface in the same time, and the consequence would 

 be that the gas would escape hotter ; just as, in the case of a 

 steam boiler, a small extent of boiler surface caused a hot chimney. 

 This question however was independent of the chemical advantages 

 that might be obtained by hard driving. 



Mr. C. "W. Siemens thought the illustration suggested of the 

 firebrick regenerator in the hot-blast stoves was not a parallel 

 case, because the area of cooling surface of the firebrick in the 

 regenerator was practically unlimited, on account of the means 

 afforded of reversing the direction of the current through the 

 regenerator as often as desired, whereby the points of maximum 

 and minimum heat might virtually be separated by any distance 

 required. There was no means of taking up a greater quantity of 

 heat from the escaping gas in the blast furnace, because there was 

 only a limited quantity of material, which was heated by a fixed 

 quantity of gas ; for although in any particular quarter of an 

 hour it might be possible to fill in more material than corre- 

 sponded to the average rate of smelting, yet in the course of 

 a week the total quantity of ore put in was exactly the quantity 

 smelted ; and for absorbing the extra heat generated in smelt- 

 ing 1 cwt. of ore at the bottom of the furnace it was not 

 possible by any means whatever to add more than 1 cwt. of 

 fresh ore at the furnace top, with the proportionate quantity of 

 the other materials. 



Mr. C. W. Siemens remarked that at the previous meeting, 

 while appreciating the value of the facts brought forward in the 

 paper then read, he had been unable to agree with the conclusion 



