"Do you know, Norah," said Willie, "which is the best of all the metals?""I should think gold is the best," said his sister; "it is worth so much money, and is so bright and beautiful.""No," said Will, "gold is not the best metal. Iron is the best, because it is so useful. Teacher says it is the King of Metals. We see more things made of iron than of any other metal. Here comes Fred. Suppose we have a chat about iron now.""All right," said Fred, "I"m ready. Where did this iron poker come from at first, Norah?""The iron was dug out of great pits in the earth, called mines," said Norah. "That is why we say iron is a mineral.""That"s right," said Fred, "but the iron was then only like a rough stone. It was called iron-ore or iron- stone. Much has to be done to make it fit for use.
"The iron-stone is first mixed with coal, and piled in great heaps in the open air. The heaps areset on fire and left to burn for days. This is called roasting the ore. It bur ns away the sulphur and some of the other useless parts of the ore. Theroasted iron-stone is next put into the blast furnace. This great furnace is made of solid stone and brick- work, built in the form of a cone or sugar-loaf. Just think of a great sugar-loaf seventy feet high, Norah.""Teacher showed us a picture of a blast Furnace," said Will. "It was so easy to understand all about it from the picture. It looked as if the great furnacehad been cut down through the middle, from the top of the cone to the ground.
"There was a gallery all round the top, and we could see the men on the gallery wheeling barrows filled with iron-stone and fuel. The furnace is always fed from the top. Every half hour the men throw in their barrow-loads of iron-ore, coke, and lime. The furnace burns day and night, and is never once allowed to go out for years.""I suppose the great heat melts the iron in the ore," said Norah, "for iron is fusible.""Quite right, little sister," said Fred, "and the melted iron sinks to the bottom of the furnace, because it is heavier than the other substances."SUMMARY
Iron is the " king of metals." Iron-stone or iron-ore is dug out of the earth. It is ?rst mixed with coal, and roasted in great heaps. Then it is smelted in the blast furnace with coal, coke, and lime. The enormous heat melts the iron of the ore, and it sinks to the bottom of the furnace as a thick, red-hot liquid. All the useless parts of the ore ?oat on the top of the liquid iron.
Lesson 23
Iron
"Fred," said Norah, "do tell me what becomes of that melted iron at the bottom of the blast furnace.""There is a hole in the side of the furnace," said Fred. "The men keep it plugged up close and strong with fire-clay. Every twelve hours they come with long iron rods, and break away this clay plug. Then of course out comes the red-hot liquid iron.
"The floor all round the furnace is laid thick withsand, and channels about four inches wide are made in the sand. As the red-hot liquid metal flows out through the hole in the furnace wall it runs intothese moulds of sand. When it gets cold it forms solid blocks of iron. The blocks are called pigs of iron. The iron itself is known as pig-iron. It is also called cast-iron, because it is cast or poured in the liquid state into the sand moulds, and left to cool.""And is this pig-iron fit now to make all sorts of things?"" asked Norah.
"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
The red-hot, liquid iron is run off from the bottom of the blast furnace, just as we might run off water, or any other liquid, from a tap. It flows into sand molds on the floor, and when it is cold it forms great blocks or pigs of cast-iron. The pigor cast-iron is again melted in great pots, in the puddling furnace, and left to cool, after which it is heated till it is red- hot and pliable, and in that state it is beaten for a long time with immense hammers, and cut up into bars while it is soft. It is then called wrought iron.
Lesson 24