224 HANDBOOK OF NATURE STUDY 



any acre of dry ground ; every shower washes the excavated 

 soil away and closes the holes, but the next sunny noon 

 finds our pigmy miners diligently at work reconstructing 

 their Lilliputian galleries. When we remember that worms, 

 insects, and mammals had cultivated the soil for thousands 

 of years before man began to use rude ploughs and hoes, it 

 is plain that near the surface there exists probably little soil 

 which these humble creatures have not turned over. They 

 have done their share to make this earth a place Jit for human 

 habitation and human activity. Should we now begrudge 

 them their homes, where they work and are happy in their 

 own ways, when they do not injure us ; should any boy or 

 man be so brutal as to wish to shoot, kill, or crush every- 

 thing which flies, walks, or creeps ? 



To our shame it must be acknowledged that there are not 

 only such boys, but also such men still among us. 



40. Field and Garden Soil. 



MATERIAL, : About a quart of black soil mixed with gravel and 

 pebbles ; pieces of crumbling and decaying stones ; a half-gallon glass 

 jar ; a large flower pot. Observed outdoors : Black topsoil ; sandy 

 and clayey subsoil ; humus from woods or swamps. 



It is known to everybody that animals live on the sub- 

 stances they take into their stomachs, and that indigestible 

 matter is passed off with the excrements. It has been a 

 more difficult matter to find out just! how plants feed ; but 

 careful experiments have shown that most of the substance 

 which makes the woody tissue of plants is absorbed from the 

 air by the leaves. If you put a piece of wood into a hot 

 oven until it becomes charred, you will see that wood con- 

 tains a large part of coal. Green leaves absorb carbon 

 dioxide gas from the air, and in this carbon dioxide gas the 

 coal is contained. If a plant is kept stripped of all its 

 leaves, it will die of starvation. What insects frequently 



