Handbook of Nature-Study · Lesson CCIX · Topic 32: The brook
209. The brook
Goal: Your child can follow a brook toward its source and explain how running water carries soil away and wears its banks.
You'll need
- A brook you can reach safely with an adult
- A clear glass jar with a lid
- A watch or timer and a tape measure
- A cork or a stick to float
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
Part IV, Earth and Sky, opens with this lesson. It has a leading thought and sixteen observations on the brook's source, banks and bends, where it flows, its color in flood, the soil it carries (with a jar experiment), how fast it runs, a map, and the life along it, ending with a "brook puzzle."
The lesson, step by step
Safety first, and when to go
Stay out of a brook that is flooded, fast or muddy, and away from steep or undercut banks, which can give way. The book suggests reaching into a flooded brook and wading in it to feel the pebbles; we don't do that. Watch from a firm bank, and wade only in a shallow, calm brook at its normal level, with an adult and water shoes. Wash hands afterward.
The book says the best time is after a rain, and October or May is a good time to begin. Come back through the year to see how the brook changes.
The leading thought
The water from the little brook near our schoolhouse is flowing toward the ocean, and is meanwhile digging out and carrying along with it the soil through which it flows.
Where does it start? Where does it go?
Does the brook have its source in a spring or a swamp, or does it receive its water as drainage from surrounding hills?
If you should launch a toy boat upon the waters of this brook, and it should keep afloat, through what streams would it pass to reach the ocean?
Trace the route together on a paper map or an online map.
Banks and bends
Is the course of the brook more crooked on a hillside or when flowing through a level area?
Can you find the places where the water is cutting the banks most, when the brook is flooded? Why does it cut the banks at these particular points?
What is it carrying?
After a rain, when the water is muddy, an adult dips the jar from the edge of the brook.
Place it on a window-sill and do not disturb it until the water is clear. How much sediment has settled at the bottom of the jar? Where was this sediment when you dipped up the water?
How fast?
To test the rapidity of the current, put something afloat on it and measure how far it will go in a minute.
Toss the cork in upstream and walk beside it along the bank.
The brook puzzle
Read the book's puzzle aloud and let your child think about it:
How is it that in the case of a brook just opposite is true? The faster the brook runs, the more it can carry; and the heavier it becomes the faster it runs; and the faster it runs the more work it can do.
Nature notebook
Draw a map of your stretch of brook showing its bends, pools and the swiftest current. Add the jar of settled mud as a little picture, and the speed you measured.
Afterwards
Visit after a big rain and on a dry day; compare the color, the sound and the speed.
Answers to the book's problems
The brook cuts hardest on the outside of its bends, where the swift current strikes the bank; that cutting makes the bends bigger. Bare banks give more soil than banks held by roots. The puzzle: a brook is not carried along by legs; gravity pulls the water downhill, and more water and a steeper slope make it flow faster, and fast water has the force to lift and roll a heavier load.
Worked out for this site from the scan. If a number in your copy differs, trust the book.