Earth Sttuty 84 S 



Humus is composed of decayed animal and vegetable matter. It is very 

 rich in plant food. Wherever there is humus in the soil it is likely to be 

 darker in color than the stone flour. 



Loam is a mixture of clay, sand and humus. For many crops it is the 

 most desirable soil. 



LESSON CCXX 

 The Soil 



Leading thought — The soil is composed of rock flour and humus. Soil, 

 to support life, must be porous, so that the roots of the plants may receive 

 through it both water and air. 



Method — The children should bring in specimens of soils from various 

 localities near the school. Parts of each specimen should be wet to see if 

 they are clayey, that quality showing quickly in the puttylike adhesiveness 

 when rubbed between the fingers. It would be well to get some pure blue 

 clay, and let the children make marbles of it to impress upon them this 

 quality of clay. They should try and make marbles of other soils to show 

 the lack of adhesiveness in them. They should examine sand through a 

 lens and should examine humus in a similar way. After they are familiar 

 with these three kinds of soils, they are ready for the lesson. 



Observations — i . Look at any kind of soil with a lens, and tell why you 

 think it is made up of small pieces of stone and rock. 



2. Take a piece of rock and pound it fine. What does it look like? 

 Do you think that your plants will grow well if you plant them in the rock 

 flour which you have just made? Try the experiment and describe the 

 results. 



3 . How does the water grind off the stones and make soil ? How does 

 the wind do it? 



4. How do water and frost pry off pieces of rock. Is there a cliff in 

 your neighborhood that has at its foot a heap of soil and stones ? Where 

 did these comes from? 



5. How do the lichens and other plants pry off the outside of rocks? 

 Have you ever found lichens growing on stones? 



6. Have you ever noticed old headstones in the cemetery that were 

 falling to pieces ? What causes them to decay ? 



7. Write an English theme on the great glacier that formerly covered 

 the northeastern portion of the United States. 



8 . Go to the woods, scrape off the leaves and get some of the black earth 

 beneath them. Of what is this soil composed? Is it rock flour? What 

 makes it so black ? Why do you call this soil rich ? What does it do if you 

 add it to the soil in the pots where your flowers are growing ? 



9. Find a railroad cut or some other place where the earth is exposed 

 for some distance up and down. Is there solid rock at the bottom ? How 

 deep is the soil above the rock ? Is the soil the same color at the surface as 

 it is below ?> Why is this ? 



10. Experiment i: To show which kinds of soil hohl most water — Take 

 three lamp chimneys, or bottles from which the bottoms have been broken. 

 Place in one loam in another clay, in another fine-grained sand, using in 

 each case the same amount. Tie cheesecloth over the bottom, so that the 

 soil will not fall out; make the soil compact by jarring down. Place each 

 over a tumbler. From a cup of water, held as near as possible to the soil, 

 pour water into one of the bottles slowly, so as to keep the surface of the soil 



