L ET us have another chat about the river. We may fancy that we are following it in its course to the sea. We shall then learn for ourselves many things we do not know about rivers.
We will begin our journey at its source. Here it is a little rill, formed by water that trickles from a spring, or by the melting of snow.
As it flows on, it is joined by many other little streams, until it grows to be much larger.
There is a large word used for a stream that feeds another stream. Do you know what it is? The word is tributary. Tributaries are often called branches.
Before we leave this part of the river, I wish you to learn another hard word.
You have seen the water run off the roof of a shed. The ridge; or highest part of the roof, divides the rain that falls on it, so that part of the rain flows down the one side, and part of it flows down the other side.
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.
Hills send off streams on both sides.
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?
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.
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.