\/A> WILLIAM SIEMENS, F.R.S. 221 



temperature of the flame, that renders it so difficult to maintain a 

 high heat by gas of this description burned in the ordinary way. 

 In u>ing such gas in a regenerative furnace the presence of so 

 large an amount of nitrogen is not objectionable, as the heat it 

 ies off' is given up again to the air and gas coming in. 



The gas as it passes off from the fuel contains also more or less 

 aqueous vapour, which is got rid of by cooling it, with some tar and 

 other impurities, and a small quantity of suspended soot and dust. 



Any air drawing in unburned through a hole in the mass of 

 fuel, reduces the value of the gas, by burning the carbonic oxide 

 again to carbonic acid. To prevent the indraught of air in this 

 way at the side of the grate, I have found it very advantageous to 

 set the side walls of the gas producer back, forming a broad step, 

 about nine or ten inches above the grate ; any air creeping up 

 along the wall is thus thrown into the mass of fuel and completely 

 burned. The effect of this feature in the form of the producer on 

 the quality of the gas has been very striking. 



Three-tenths of the total heat of combustion of solid carbon are 

 evolved in burning it to carbonic oxide ; but in the gas producer, 

 a small portion only of "this heat is really lost, because it is in a 

 great measure taken up and utilized in distilling the tar and 

 hydrocarbon gases from the raw fuel ; and it may be still further 

 economised, especially in burning a fuel, such as coke or anthra- 

 cite, which contains little or no volatile matter, by introducing a 

 regulated supply of steam with the air entering at the grate. This 

 is effected very simply by keeping the ash-pit always wet. The 

 steam is decomposed by the ignited coke, and its constituents, 

 hydrogen and oxygen, are rearranged as a mixture of hydrogen and 

 carbonic oxide, with a small variable proportion of carbonic acid. 

 Each cubic foot of steam produces nearly two cubic feet of the 

 mixed gases, which, being free from nitrogen have great heating 

 power and form a valuable addition to the gas. The proportion 

 of steam that can be advantageously introduced into the gas pro- 

 ducer, is, however, limited, as it tends to cool the fire, and if this 

 is at too low a heat, much carbonic acid is produced instead of 

 carbonic oxide, causing waste of fuel. 



From the high temperature of the gas, as it rises from the fuel 

 (1,000 F. to 1,300 F.), and from its comparatively low specific 

 gravity, it is considerably lighter than atmospheric air, and 



