More about Things Found in the Earth
W E have seen that there are many kinds of metals. There are also many kinds of stone. Those which are strong and do not crumble by exposure are useful for building. The place from which stones are taken for building is called a quarry.
The more common stones are granite, sandstone, limestone, marble, and slate.
We will first examine a piece of granite. How hard and firm it is! What a beautiful clean surface when polished!
Granite is used for steps, for paving streets, and for sidewalk curbings. Are houses ever built of granite? Can you think of other uses of granite?
Why is granite used for these purposes? It is easily shaped. It is hard enough to give strength. It is enduring. What does "enduring" mean?
This is a piece of sandstone, made of little grains of sand. It will crumble more easily than granite. What does "crumble" mean? Brownstone, used in building, is a kind of sandstone.
And this is the common gray limestone of which lime used in building is made. The large oven in which lime is burned is called a lime-kiln. Did you ever see one? Can you tell how the lime is made?
Here are three pieces of marble. This piece is pure white. This is colored. It is marked by many strange forms, as you see in your mantel-pieces and table-tops. In this piece, you see many colored spots—mottled it may be called.
Marble is beautiful when polished.
In what different ways have you seen marble used? What parts of furniture are sometimes marble? Why is it suitable for this? Is marble ever used for building houses? Do you think it would be good for that purpose? Why? Which, do you think, is the best of all building stones? Why?
Marble and granite are the most beautiful and enduring of all building stones.
Chalk is a variety of limestone. Could it be used as a building stone? Is chalk harder or softer than other stone?
You need not to be told the name of this dark stone. You could not get along well in school without slate. Slate is easily split into thin plates, and has a smooth, firm surface.
Slate is used to write on. It is used in house building. What part of a house is sometimes slate? Think of other uses. Why is it useful for these purposes?
We must not forget brick in our talks about things that come out of the ground. Brick is not found in the earth, as the metals and stone are found; but it is made of clay, which is itself a part of the ground.
Have you ever seen a brick-yard? What are some of the uses of bricks? What is the man called who builds houses of bricks?
Is glass taken out of a mine or quarry? No; but glass is made from sand; which is also a part of the ground.
In laying brick or stone, the mason uses mortar. Mortar is made chiefly of lime. Lime is made of stone which comes out of the ground.
If possible, visit mines and quarries. Take careful notice of all you see, and on your return to school tell what you have learned.