S/K WILLIAM SIEMENS, F.R.S. 22$ 



ami from these we have, on the one hand, the increase of pressure 

 J.:T loot of height, in a flue rising directly from the gas producer, 

 = -on; ( '!'_' = M).H ll>. per square foot; and on the other 

 hand, tip- excess of pressure at the foot of the downtake from the 

 cooling tube, over that at the same level in the flue, leading up 

 from the gas producer (for each foot in height of the cooling 

 tub.-) = -OG1 '022 = -039 Ib. per square foot. The height of 

 the cooling tube above the level of the flue that will be sufficient 

 to produce the required pressure, equal to 10 feet of heated gas 



column, is therefore '. - . 10 ft. = 13' 10", or say 14 feet. 



'OoJ 



This method of obtaining a pressure in the gas-flue by cooling 

 the gas, has been objected to as throwing away heat that might be 

 employed to more advantage in the furnace, but this is not the 

 case, because the action of a regenerator is such, that the initial 

 temperature of the gases to be heated has no effect on the final 

 temperature, and only renders the cooling of the hotter fluid more 

 or less complete. The only result, therefore, of working the 

 furnace with gas of high temperature is to increase the heat of the 

 waste gases passing off by the chimney flue. The complete cooling 

 of the gas results, on the other hand, in the great advantage of 

 condensing the steam that it always carries with it from the gas 

 producer ; and in the case of iron and steel furnaces, in burning 

 wet fuel, it is absolutely necessary to cool the gas very thoroughly, 

 in order to get rid of the large amount of steam that it contains 

 which, if allowed to pass on to the furnace would oxidise the 

 metal. 



There is, undoubtedly, a certain waste of heat, which might 

 be utilized by surrounding the cooling tube with a boiler, or by 

 otherwise economising the heat it gives off, as, for instance, in 

 drying the fuel ; but the saving to be effected is not very great, 

 for as 100 volumes of the gas require for combustion about 130 

 volumes of air, including 20 per cent, above that theoretically 

 required, the heat given off in cooling the gas 1,000 is no more 

 than would be lost in discharging the products of the complete 

 combustion of the fuel, at a temperature 435 in excess of the 

 actual temperature of 200, and this loss is greatly diminished if a 

 richer gas is obtained. 



In erecting a number of gas producers and furnaces, I generally 



