to mighty machines, does more work than thousands of men and
horses.

These machines produce paper, cloth, flour, lumber, and many other
useful articles.

When water is heated and turned into steam, it moves powerful engines.
These engines propel our great steam-ships and steam-boats and drive
machines of all kinds in mills and factories.

Many of you have seen water, clear and cool, trickling from the rocks in
the side of a hill. This water first forms a spring.

From this spring, the water escapes in a tiny stream, called a rivulet
or creek, and flows along until it enters a river. Many springs make
many rivulets; many rivulets make large rivers.

Rivers sometimes receive such great quantities of water that they
overflow their banks, and destroy much valuable property. This is called
a freshet or a flood.

Many people who live near some of our rivers have lost their houses,
furniture, and cattle, which were all swept away by these floods.

In the winter of 1883, the Ohio River received so much water from the
thousands of rivulets flowing into it, that it overflowed its banks.

The result of this overflow was one of the greatest floods ever known,
and many, no doubt, who read this, were there to see its terrible
effects.

But where does all this water come from? you may ask.

Let me see if I can explain it to you. The water in all these rivers,
lakes, and oceans is constantly rising into the air in what is called
moisture or vapor. We can not see this moisture, neither can we see the
air.

If the air is cold, moisture does not rise rapidly; but, as the air
becomes heated, it takes up more moisture, so that the more heat there
is in the air, the more moisture rises.

Heated air is light, and rises higher and higher from the ground, taking
the moisture with it, until it reaches a point where it begins to cool.

Then as the air cools, the moisture forms into clouds, and these clouds
are, in a certain sense, floating water.

Floating water! How can water float! do you ask?

Well, I will tell you. Cold air is heavier than heated air, and until
the clouds become so full of moisture as to return some of it to the
earth, in the shape of rain, they float because they are lighter than
the air underneath them.

The winds, by the flapping of their mighty wings, drive the clouds over
the land to the hills and the mountains and the thirsty fields; and
there they pour their blessings on the farms, pastures, orchar