2 Field Museum of Natural History 



stone and form a slag which melts and runs from the 

 furnace. The furnace runs continuously day and 

 night from the time it is blown in until it is necessary 

 to shut down for repairs. As the charge wastes away 

 below it is replenished by additions of ore, limestone 

 and fuel from above. 



The model represents in some detail the furnace 

 in which the smelting is accomplished and some of its 

 accessories. At the center of the model is a circular 

 tower which houses an elevator by which materials to 

 be fed to the funiace are lifted to the top. At the left 

 of the elevator is a blast furnace and some of its ac- 

 cessories. At the right the furnace and accessories 

 are repeated in section, that is cut open to show the 

 inside. 



THE FURNACE or STACK is a tall structure of 

 brick enclosing a central shaft lined with the best 

 quality of fire-brick and cased on the outside with 

 boiler iron. This furnace is sixty-five feet high and six- 

 teen feet wide at its widest part. Many furnaces are 

 larger than this. The disk-like structure which rests 

 on top of the furnace is a circular room of boiler iron 

 which encloses the CHARGING PLATFORM from 

 which the furnace is fed. The material fed to the 

 furnace is the CHARGE. The charge is a mixture in 

 carefully proportioned quantities of ore, flux and fuel. 

 THE ORE is a combination of iron and oxygen and is 

 the source of the iron which is the product of the fur- 

 nace. THE FLUX is limestone. This combines with 

 any infusible matter which may form in the furnace, 

 causes it to melt and washes it from the furnace in the 

 form of slag. It also prevents waste of the iron of 

 the ore and serves other useful purposes. THE FUEL 

 is generally coke although some few furnaces use char- 

 coal. The fuel provides the necessary heat and also 

 the reducing gases which free the iron from the ore. 



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