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Brook Basins And Systems

( Originally Published 1891 )



"Thou, ever joyous rivulet,
Dost dimple, leap, and prattle yet ;
And sporting with the sands that pave
The windings of thy silver wave,
And dancing to thy own wild chime,
Thou laughest at the lapse of time.' "

- BRYANT.

THUS sang the cheerful robin, while he flew down to join his friends by the brookside, next morning, as Bunny asked the silvery drops to tell how they found their way out of the cold ground.

" 0, that was easy enough. We just ran along till we found a place where the clay-bed came to the surface on the hillside."

" But how did you . know which way to flow?" chirped the robin.

" At first we did not know. But when many raindrops met on the bed of clay, we soon found a way. Isn't it strange that in this wide world of ours, there is no level land where the raindrops fall ? "

" Ho, ho, Master Brooklet ! " cried Dick.

"Where are your eyes ? Our own meadow is just as level as the pond."

But the watchful wild-flower knew better than that. Had it not seen the dimpled waves go dancing by all summer ?

" Can you tell me why our brook doesn't flow the other way, Dick ? " it whispered softly.

Chip, chip ! hurrah for posy ! " sang a merry voice from under the leaves.

You are right, little flower," bubbled the stream. I could not move if the meadow were level. In the open air I must flow down the slopes, except when the sunbeams spread my vapor-wings. Where water runs, the land must change its level."

" But wait," replied Dick. Here is a pond in which the water only stands, and does not flow away." Then he blinked his bright eye as if to say, " How do you explain that ? "

The wild-flower only nodded and asked, " Why does it not spread out evenly over the whole meadow ? "

"Because the banks hold, oh, I see!" said the honest squirrel. " The land must slope towards the pond. Our meadow looks level, but it must slope a little. If the meadow were as high in one place as in another, the water could not drain away, could it ?

" Then there would be no brooks, no ponds, only muddy fields. The whole surface would be covered with water. All the plants would die. There would be no hills, no valleys, no streams. Poor Bunny could not dig in the ground, and I don't know what the squirrels would find to eat. Why ! the salt ocean would flow over the land, and then but we need not think of that, for the fields do slope."

" Yes," added the brook, even the beds of rock and clay beneath the surface slope. That is how the raindrops got out of the dark soil. We just ran along on the clay-bed, and leaped into the warm air.

" When there has been no rain for weeks, the water that is in the soil keeps flowing out. The ponds and marshes also give up their store of water, and the streams flow on during the dry season.

" Which of you can tell me how much land is drained by our brook ? "

" All the land in the valley sends its water to the brook-bed," piped the robin.

" You must drain all the slopes on this side of the highland," said Chip.

"All the land that slopes downward to the brook-bed must send its water into the brook," added Dick.

" The whole basin within the water-parting must drain into our brook-bed," was Bunny's answer.

Is every basin bounded by a water-parting ? " asked the wild-flower.

"Yes, every basin on earth," rippled the stream. " Beyond the hill, there is another valley in which Dick saw a brooklet flowing. The slopes that meet to form its bed stretch upwards on both sides till they reach the rims of other basins.

"The upper edges of these slopes are water-partings, or lines of highest level, between the valleys.

" Little rills have basins also, bounded by lower water-partings ; and so have ponds, lakes, rivers, and even the great oceans. The surface of the whole earth is made up of basins and beds surrounded by a network of water-partings.

" Now let us begin at the rim of our valley and trace all the streams. First, there are the tiny rills that trickle among the grasses during a rain-storm, and form the thread-like rivulets. Then these little streams wind about to join our brook.

"All the streams together form a 'system,' by which the valley or basin is drained. A system in a brook basin is called a ' brook system' ; in a river basin, a ' river system.' Thus we may have also a ' lake system,' or an ocean system.'

" Then there are other streams that belong in our brook system, but which we cannot see. They are the tiny rills that flow underground and feed the springs. We must not forget these little branches, for they are as useful as the surface rills.

" Between a basin and its system there are lines which we call ' shores.' They are the lines along which the slopes pass under the water, or the lines which show how high the water rises in the beds. Shores are the boundary lines of beds. They are also the lower edges of basins. A shore separates a bed from a basin.

" If we wished to be very exact, we should perhaps say that a basin is bounded at its upper edge by a water-parting, at its lower edge by a shore, and that the basin is made up of the slopes that lie between.

"Now I have a few questions to ask you, and then I will tell you of a great river valley that I saw a few years ago, far away towards the midday sun.

" What is the difference between a basin and a system?"

" A basin is land, and a system is water," said Chip.

"I should say that a basin is made of slopes, and a system of streams," was Bunny's answer.

"Doesn't a system carry water away from a basin?"

" It does, bright flower," replied Dick. "I do hope that you will grow here again next summer. We should be very lonely without you. I shall look for you as soon as the snow melts."

The pretty wild-flower trembled, it was so happy. Then it nodded its little head as if to say, " Yes, I will try to be here with you all."

Just then the brooklet asked another question : " Have the basins of all our rivulets the same shape?"

" 0, no !A chirped the robin. " I saw one, as I came along this morning, that spreads out like a maple-leaf. It is near the old pine, and is as long as it is wide."

" Near the large spring there is a basin that lies among a group of knolls," said Bunny. "There is a long narrow valley leading from it towards the meadow. The upper part of the basin looks like a water-lily leaf, with the narrow valley for its slender stem. The tiny streams that flow in it look like a beautiful vase-shaped elm with wide-spreading top on a long trunk."

"Between the two bluffs, on the east side of the pond, there is a very long basin that is shaped like a blade of grass," added Dick. " And there is another very queer one in the rough land near the spring. It is like a row of leaves on a single stem. There are four round valleys joined by narrow gullies. In each valley there is a small pond, but one slender stream runs through all."

" You have sharp eyes, my friends," rippled the brook. " There are hundreds of basins shaped like each of these, and so we will call the valleys of our little rivulets ' types ' of the great river basins that cover the earth's surface. Now for my story of the Amazon :

"It is nearly midday, and if Redbreast should fly far south to the land just under the sun, he would see hundreds of white-capped mountains. They are many times higher than the one which he flew over in the storm.

"All along the east side of this great highland there are countless streams flowing in as many basins. If we could see ten times as far, we could see ten times as many.

"Down the steep slopes they run, sparkling in the clear sunlight. Here and there they flow together, just like our slender rivulets, only many times wider and deeper.

"Now they enter a dense forest, and from all sides other streams come in, till they form a great river. Its basin is so wide that we cannot see across it.

" On, on, for days and weeks, it winds along a low plain, through a forest so thick that the sun-light can scarcely creep in. Again and again great rivers flow in, till it looks like a vast sea. Its basin is so wide that if our robin should fly all day and all night he could not cross it.

At length the mighty stream pours its muddy water into the dark-blue ocean, and the raindrops that fell on the distant mountain sides have reached their home. All the rills and rivulets, brooks and rivers, that join to make this great stream belong to the Amazon system; while every slope that sends one drop of water towards the dark forest, and into the broad river, is a part of the Amazon basin."

As the brooklet ended its story, the sun sank slowly behind the low hills. The evening breeze came floating into the valley, and seemed to whisper

"The day is done; and the darkness
Falls from the wings of night,
As a feather is wafted downward
From an eagle in its flight."

-LONGFELLOW.



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