THE SUMMER STREAM.
Let us visit the river upon a summer day. It is no longer a muddy torrent. In fact the stream is so different that we hardly know it. The clear water ripples gently. We can see the sand and pebbles in the bottom. Little fish are darting here and there.
The river is doing no work now. The summer is its resting time. There are many kinds of pretty pebbles in the water. They are almost as round as marbles and very smooth.
Such interesting stories they can tell. Each little pebble has a different one. They were once pieces of rough rock in the mountains at the head of the river.
One piece fell from a rocky cliff and rolled into a dashing stream. Another piece was picked up by a little boy and thrown into a canon. A third came from a tunnel where miners were at work. It rolled down the mountain and into a creek.
As winter came the little streams in which the pieces of rock lay were turned into dashing torrents. The pieces were rolled over and over for many days, but when summer came the water went down and they rested for a while.
At last they reached the main river. They were much changed. Their corners were gone and they began to look like pebbles. Year after year the pieces of rock became smoother, and one summer they were dropped where you saw them. Another winter they will again be moving down the river, rolling and tumbling along in the muddy water.
Place some bits of rocks in a dish and shake it for a few moments. You will find that the corners of the pieces have been rubbed off a little and that there is dust in the bottom.
Why is the river water so clear in the summer? We can find out by following the river to its head, The river divides into many little streams. At the head of each there are clear springs.
Spring water has come a long journey through the ground. It has lost all the mud which it had when on the top of the ground. The spring is filtered rain water. If you turn muddy water into a filter it comes out clear. In the filter there is either sand or rock fUll of tiny holes. Passing through these the water loses its mud.
The river is muddy in the winter time, for then it gets the most of its water from the top of the ground. You know kow dirty the ground is.
In some countries the rivers disappear in the summer. The thirsty air keeps taking the water as long as there is any in sight. If the river bed is sandy a part of the water escapes. It creeps in among the sand grains away from the sun and air. People obtain water from such a river by digging holes in the sand.