S/X WILLIAM SIEMENS, F.R.S. 385 



t'l-- apparatus in which the solid is converted into gaseous fuel. 

 This is a very simple apparatus, consisting of a cubical brick 

 chamber of about 8 feet side, one side of which is cut off in a 

 slanting direction. Fuel descends on this inclined plane, to the 

 grate at the bottom where combustion takes place. The result of 

 this combustion is carbonic acid at a high degree of temperature, 

 ami if this product of combustion was allowed to pass up the gas- 

 collecting channel, and through the overhead tube to the furnace, 

 there would be nothing to burn ; and the only result we should 

 probably observe would be that the iron tube would very soon 

 become red hot, and be melted down. But the carbonic acid as 

 it is formed near the grate, encounters a further layer of fuel 

 descending from above, which is also incandescent, but which 

 cannot be consumed on the same terms, because there is no longer 

 any free oxygen present The first result of combustion being 

 carbonic acid, a compound of one atom of carbon and two of 

 oxygen, this carbonic acid in passing through the subsequent 

 layers of incandescent fuel is broken up, and a second molecule of 

 carbon is added to the first, thereby producing carbonic oxide, 

 which is a combustible gas. But coal is not simply carbon, it 

 consists also of volatile matters, hydro-carbons, water, and the 

 constituents of ammonia, and the hot carbonic oxide in passing 

 through a further thickness of the fuel which contains these 

 gaseous constituents, acts upon them in the same manner as heat 

 does upon the coal in a gas retort. This action absorbs a portion 

 of the free heat in the carbonic oxide, and the result is a gas 

 consisting of carbonic oxide, hydrogen, hydro- carbons, aqueous 

 vapours, and nitrogen, which latter, being a constituent of atmo- 

 spheric air, necessarily passes with it through the fuel, and dilutes 

 the combustible gas produced to the extent of about 50 per cent, 

 of the total volume. This combined gas leaves the producer not 

 at 3,000, the temperature of direct combustion, but at about 

 700 F. only. This remaining heat is thrown away and purposely 

 so, and many criticisms have been made in consequence of this 

 apparent waste of heat in the regenerative gas furnace, but I 

 think I can prove that although there is loss of heat, no waste is 

 incurred. 



The gases passing from the gas-producer could be forced to the 

 furnace by mechanical means, but this would be very troublesome 

 VOL. i. c c 



