220 THE SCIENTIFIC PAPERS OF 



of the incline at A, and falls in a thick bed upon the grate. Air 

 is admitted at the grate, and as it rises slowly through the ignited 

 mass, the carbonic acid, first formed by the combination of the 

 oxygen with the carbon of the fuel, takes up an additional equiva- 

 lent of carbon, forming carbonic oxide, which diluted by the inert 

 nitrogen of the air and by a little unreduced carbonic acid, and 

 mixed with the gases and vapours distilled from the raw fuel during 

 its gradual descent towards the grate, is led off by the gas flue to 

 the furnace. The ashes and clinkers that accumulate on the grate 

 are removed at intervals of one or two days. 



The composition of the gas varies with the nature of the fuel 

 used, and the management of the gas producer. That of the gas 

 from the producers at the Plate Glass Works, St. Gobain, France, 

 burning a mixture of f caking coal and \ non-caking coal, is as 

 follows, by an analysis dated July, 1865 : 



VOLUMES. 



Carbonic oxide . 23"7 



Hydrogen . . . . . . . . 8'0 



Carburetted hydrogen . . < . .2*2 



Carbonic acid 4'1 



Nitrogen ..... ... 61'5 



Oxygen 0'4 



99-9 



The trace of oxygen present is no doubt due to carelessness in 

 collecting the gas, or to the leakage of air into the flue, and 

 allowing for this, the corrected analysis will stand as under : 



VOLUMES. 



Carbonic oxide 24'2 \ 



Hydrogen 8'2 / 34'6 



Carburetted hydrogen . . . 2'2 ] 



Carbonic acid . . . . . 4'2 



vr-i. fi . > f G5'4 



Nitrogen (>1 



lOO'O 



Only the first three of these constituents, say 35 per cent, of the 

 whole, are of any use as fuel, the nitrogen and carbonic acid 

 present only diluting the gas. It is the presence of this large 

 proportion of inert gases, which must be heated to the full 



