GAS-FURNACE 



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tible gas) thereby produced, in passing slowly on through a layer of incandescent fuel 

 from 2 to 3 feet thick, takes up another equivalent of carbon, and is thus transformed 

 into carbonic oxide (an inflammable gas), which passes off with the other combustible 

 gases to the furnace. For every cubic foot or combustible carbonic oxide thus pro- 

 duced, taking the atmosphere to consist of l-5th part by volume of oxygen and 4-5ths 

 of nitrogen, two cubic feet of incombustible nitrogen pass also through the grate, tend- 

 ing greatly to diminish the richness or heating power of the gas. Not all the carbon- 

 aceous portion of the fuel is, however, volatilised on such disadvantageous terms ; for 



1059 



water is brought to the foot of the grate by the pipe E, which, absorbing the spare heat 

 from the fire, is converted into steam ; and each cubic foot of steam in traversing the 

 layer of from 2 to 3 feet of incandescent fuel is decomposed into a mixture consisting 

 of one cubic foot of hydrogen and nearly an equal volume of carbonic oxide, with a 

 variable small proportion of carbonic acid. Thus one cubic foot of steam yields as 

 much inflammable gas as five cubic feet of atmospheric air ; but the one operation is 

 dependent upon the other, inasmuch as the passage of air through the fire is attended 

 with the generation of heat, whereas the production of the water-gases, as well as the 

 evolution of the hydrocarbons, is carried on at the expense of heat. The generation 

 of steam from the water being dependent on the amount of heat in the fire, regulates 

 itself naturally to the requirements ; and the total production of combustible gases 

 varies with the admission of air. And since the admission of air into the grate depends 

 in its turn upon the withdrawal of the gases evolved in the producer, the production of 

 the gases is entirely regulated by the demand for them. The production of gas may 

 even be arrested entirely for twelve hours without deranging the producer, which will 

 begin work again as soon as the gas-valve of the furnace is re-opened ; since the mass 

 of fuel and brickwork retain sufficient heat to keep up a dull red heat in the producer 

 during that interval. The gas is, however, of a more uniform quality when there is a 

 continuous demand for it, and for this reason it is best to supply several furnaces from 

 a nest of gas-producers so as to keep them constantly at work. A damper D, shown 



