LESSON XLII.
MORE ABOUT THINGS FOUND IN THE EARTH.
| A GRANITE QUARRY |
We 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.