[Illustration:  “HILLS SEND OFF STREAMS ON BOTH SIDES.”]

Now, hills, like the roof of a house, send off streams on both sides.  When it rains, or the snow melts, some of the water goes down on one side, some on the other.  And that is why the hills which divide or part the waters of streams are called a water-parting or water-shed.

Let us now go further down the stream.

Here we see it rushing rapidly down a steep slope.  Its waters foam and dash between the great rocks that lie in the stream.  Such places in the river are called rapids.  Can you tell why they are so called?

[Illustration:  “SUCH PLACES ARE CALLED RAPIDS.”]

The stream flows on.  It has now reached a high ledge of rock.  Over this it leaps, making a great foam and noise.

When the water of a river falls over high rocks, it is called a waterfall or cataract.

You may have seen the Falls of Niagara, the greatest waterfall in the world.

[Illustration:  “YOU MAY HAVE SEEN THE FALLS OF NIAGARA.”]

The course of our river is now through a lower country.  The valley in which it flows spreads out, and the stream grows wider and wider.  The water moves slower and slower.

Why is the river swift in some places, and in others slow?

At length it flows through an almost level country.  It is here widest and deepest.  Its course is more winding.

Do you know why it is crooked and winding?

Because on the steep hillside the water runs very rapidly, and is not easily turned aside.  Where the ground is nearly level, it runs slowly, and is easily turned from its course.

LESSON XX.

THE BROOK.

      From a fountain
      In a mountain,
    Drops of water ran
  Trickling through the grasses;
    So our brook began.

      Slow it started;
      Soon it darted,
    Cool and clear and free,
  Rippling over pebbles,
    Hurrying to the sea.

      Children straying
      Came a-playing
    On its pretty banks;
  Glad, our little brooklet
    Sparkled up its thanks.

      Blossoms floating,
      Mimic boating,
    Fishes darting past,
  Swift, and strong, and happy,
    Widening very fast.

      Bubbling, singing,
      Rushing, ringing,
    Flecked with shade and sun. 
  Soon our pretty brooklet
    To the sea has run.

LESSON XXI.

WORK OF FLOWING RIVERS.

Would you like to know more about brooks and rivers—­about the work they do?

Notice what happens when it rains.  Little tiny streams are formed, which chase each other down the slopes.  See how they cut away the loose soil and carry it off.  Notice how muddy this loose soil makes the water.  What becomes of this loose soil, or mud?