"Well, no," said Fred. "Cast-iron is not fit for every purpose. These cast-iron pigs have to be melted again in great pots in the puddling furnace. This is an intensely hot furnace where a flame is made to play over the iron, although the iron itself is never allowed to touch the fuel which is burning. In theblast furnace the iron got mixed up with some of the charcoal of the coal and coke. In the puddling furnace this is all burnt away, and then the melted iron is poured out into molds. It cools in the molds and forms solid blocks of iron. But you see it is still only cast-iron.
"The blocks of iron are again put into the puddling furnace. This time the iron is not allowed to melt. It is simply heated till it is soft and plastic. Each blockis then taken out of the furnace, and beaten while it is red-hot with immensehammers worked by steam engines.
"The iron is heated and hammered in this way again and again. When it has been worked up enough, it is cut into bars while it is soft.
"It is now ready for use, and is called wrought iron."SUMMARY
