SfK WILLIAAf SIEMENS, F.R.S. 



227 





Another advantage in employing the fuel in the manageable 

 f<>rm of gas is that the rate of combustion may be regulated at 

 ire to produce an active heating flame of any length, from 

 little more than two feet, as in the pot steel-melting furnaces, to 

 thirty feet in the largest furnaces for the fusion of plate glass ; 

 and the most intense heat may be thrown exactly upon the charge, 

 the ends of the furnace and the apertures through which the gas 

 and air are introduced being actually protected from the heat by 

 the currents of unburned and comparatively cool gases flowing 

 through them, and only mixing and burning at the very point at 

 \\hirh the heat is required, and where it is taken up at once by the 

 materials to be fused or heated. This is of especial importance in 

 the case of those furnaces in which a very intense heat is employed. 



The amount of brickwork required in the regenerators to absorb 

 the waste heat of a given furnace is a matter of simple calculation. 

 The products of the complete combustion of one pound of coal 

 have a capacity for heat equal to that of nearly 17 pounds of fire- 

 brick,* and (in reversing every hour) 17 pounds of regenerator 



* Taking the analysis by Vaux of the celebrated ten-yard coal of South Stafford- 

 shire (Watts' Dictionary of Chemistry, i. 1081), the exact calculation is as 

 follows : 



Composition of the coal. 

 Carbon . 7857 



Hydrogen 

 Sulphur 



Nitrogen 



( ixy- 

 Ash 



0529 

 0039 



Oxygen required. 

 2-0952 

 0-4232 

 0-0039 



0184 



1288 . . less . . 



0103 



net oxygen required 



1 -0000 20 per cent, excess 



Total Oxygen 



Corresponding Nitrogen . . 9 '6 16 

 Nitrogen in the fuel . . -018 



2-5223 

 0-1288 



2-3935 

 0-4787 



2-8721 



Total Nitrogen . . 9 -634 



Oases produced from 1 Ib. 



of coal. 



Carbonic acid = 2'881 



Water (Steam) = 0'476 



Sulphurous acid = 0'004 



Oxygen in excess = "479 



Nitrogen = 9 '634 



Specific heats. 



217 

 480 

 154 

 218 

 244 



Equivalent weight 



of water. 



625 



228 



001 



104 



2-350 



Total equivalent weight of water .... 3 '308 

 ,, ,, firebrick (sp. heat = 0-2). 16-540 



Q 2 



