Iron is produced by smelting different ores with a flux, which extracts from them most of their impurities. The liquid iron runs out of the blast furnace into rough bars called "pigs."

1 See Part III. p. 395.

Hot Blast Iron is that produced by furnaces into which the air is admitted at a high temperature. When the air is not thus heated the resulting metal is known as Gold Blast Iron. There are but few cold blast furnaces now in the country.