18 FUEL AND FURNACES. [l. 



simple draft of air ; tlie kiln, as the lime and brick kilns, to 

 which flaming fuel is best adapted, and where the body to be 

 heated may or may not be brought in contact with the fuel ; 

 the crucible furnace, in which a crucible containing the body 

 to be melted or acted on is either surrounded by and in con- 

 tact with flameless fuel, or in the glass and pottery furnaces, 

 being at a distance from the fire, is heated by flame alone ; 

 the reverberatory furnace, in which the substance to be acted 

 on is placed on a hearth and the flame from the fire place is 

 deflected upon it by the low arched cover of the furnace ; the 

 blast furnace, in which the fuel, metallic ore, and flux being 

 mingled in an upright shaft, an intense heat is obtained by 

 forcing in a large amount of air by bellows driven by ma- 

 chinery. Although these are in general the different kinds 

 of furnaces employed, yet their forms are constantly subject 

 to variation, according to the special object in view and ac- 

 cordins: to the theoretical notions of the manufacturer. Thus, 

 when anthracite is used to generate steam, it is usual to drive 

 a larger amount of air upon it by a fan-blast than could be 

 supplied by a simple draft. Since the employment of anthra- 

 cite in the iron blast-furnace, it has been found more advan- 

 tageous to give greater width to the boshes. 



Pungernite. — This new combustible, found by Bulganne 

 in the Silurian formation of Russia, burns freely, but yields 

 less carburetted hydrogen and heat than coal. Petzold's 

 analysis (Athenaeum, 1850) gives : 



Organic matter 65.5 



Silica 13.6 



Ox. iron and alumina 2.3 



Carbonate of lime 17.0 



Carbonate of magnesia 0.2 



Water 1.2 



99.8 

 Coal. — For a full view of the statistics of coal, we refer to the 

 excellent work of Mr. Richard C. Taylor, who points out the 

 various deposits of this mineral on the surface of the globe, 



