86 



A YEAR IN SCIENCE 



from the various substances with which it is combined 

 in the ore, it is necessary to separate the element from 

 them. 



This is accomplished by heating a mixture of the ore, 

 coal or coke, and limestone in a blast furnace. The 

 blast furnace is from 50 to 100 feet high with a diam- 

 eter varying from fifteen to twenty feet. It is lined 

 on the inside with firebricks. A furnace with a body 



Courtesy of American Steel tt- Wire Co. 

 . oduces pig iron. One furm 

 with the four stoves which heat the blast. 



Fig. 36. A blast furnace produces pig iron. One furnace is shown 



rhi " 



of these dimensions will use a great deal of fuel and 

 for its combustion much air is necessary. This air is 

 supplied through pipes from the bottom under very 

 great pressure. Thus the gases in the ore are burned 



