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Slag heaps (3)
The mounds you see around you are the furnace's waste product -- slag. When iron ore is superheated in the furnace and fluxed with limestone, the molten iron sinks and impurities rise. Skimmed and discarded, the slag hardens into a glassy or airy rock similar to volcanic glass or lava rock.
Slag was removed from the furnace about every six hours and allowed to run onto the ground to harden. The large pieces were later broken and loaded into wagons for removal. Slag disposal became such a problem that slag was used everywhere to fill holes and finally just piled in heaps near the furnace. |