lead.

LESSON XLII.

MORE ABOUT THINGS FOUND IN THE EARTH.

[Illustration: 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.

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.

[Illustration: A MARBLE QUARRY.]

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 i