384 NATURE STUDY AND LIFE 



cut down until it weighs 100 grams; soak in water and 

 weigh again. We thus find that the vegetable matter in 

 the soil is one of the chief elements that enables it to soak 

 up water. 



From the data gained in the above experiments 

 encourage the children to estimate the influence of the 

 forest floor on soaking up and retaining the water that 

 falls in the form of rain or snow upon it. 



Next, ask the class to describe the springs and streams 

 in the neighborhood. This will form a valuable coordina- 

 tion with their geography lessons, and they should draw 

 maps showing the woods, springs, and streams. Ask them 

 especially to note whether the springs are muddy. Are 

 the streams of the neighborhood muddy.'' Are they 

 muddy all the time or only after heavy rains .' 



With a series of tumblers of water, into which a little 

 gravel, sand, loam, and leaf mould have been stirred, study 

 the way different materials settle to the bottom. How 

 does this illustrate the way we find such materials depos- 

 ited in sand banks along a stream .'' Some part of the 

 district may afford a good example. Let the children, 

 from time to time, bring in bottles of water skimmed 

 from the surface of the stream and have them study what 

 the stream is doing, — what it is carrying away. Wood 

 and leaves, stubble and cornstalks, with now and then an 

 acorn or a nut — everything that floats — is going down 

 stream. Examine the banks of the stream, where often 

 tons of this rich material have been lodged during a 

 freshet. Lead the class to reason from these observa- 

 tions and experiments that the best part of the soil is 

 being washed away. 



