300 ARBOR DAY 



of drought and inundations; but these apparently 

 incompatible facts are easily explained by consider- 

 ing the different effects produced by woods standing 

 in different situations. An excess of moisture in the 

 valleys comes from the drainage of the hills, and the 

 same conditions that will cause them to be dried up 

 certain times will cause them to be flooded at 

 others. Nature's design seems to be to preserve 

 a constant moderate fulness of streams and standing 

 water. This purpose she accomplishes by clothing 

 the general surface of the country with wood. 



THE FOREST SPONGE 

 From U. S. Forest Service Circular 

 WHAT child has not seen a muddy freshet? Yet 

 this sight, so common in the spring, is full of sugges- 

 tion for a forest lesson. The stream is discolored 

 by the earth which it has gathered from the soil. 

 This carries us back to the stream's source, in the 

 forest springs. Again, it shows us with what force 

 the water has rushed over the exposed ground where 

 there was no forest to shield and bind it. In just 

 this way the Mississippi tears down and flings into 

 its bed, each summer, more soil than will be dredged 

 with years of costly labor to make the Panama 

 Canal. An experiment with fine and coarse soils 

 stirred quickly in a tumbler of water and then allowed 

 to settle explains how the stream continues muddy 



