THE FOREST AS A FLOOD-PREVENTER 61 
ever the surface, the rapidity of the run-off is re- 
tarded, and the destructive influences are certainly 
lessened. 
The soil of bare regions is compacted by the beat- 
ing force of the rain. The water washes quickly over 
the surface, quickly forms torrents, and quickly 
causes washouts and destruction. The forest, by its 
shade, prevents the sudden melting of snows. <A 
considerable portion of the rain which falls is inter- 
cepted by the branches of the forest, and evaporates 
before it reaches the soil. 
Vegetation uses an immense amount of water. 
This is absorbed by the roots and transpired by the 
leaves. The transpired amount varies with the spe- 
cies of the tree, the climate, and the condition of the 
soil. In many instances it is large in amount, but 
in winter, and at times when the atmosphere is very 
humid, it is slight. The amount transpired, as with 
the eucalyptus, is often so large that soils may be 
drained by planting trees. 
Although it is possible for floods to oceur in re- 
gions which are forested, they are uncommon, and 
the damage is usually slight. Although the forest is 
only one factor in several which must be considered 
in connection with the flood question, it is neverthe- 
less an important one, as has been already proven 
to the satisfaction of the people in Europe, where 
