336 



GENERAL SCIENCE 



and they make city and country much more healthful 

 and. beautiful places in which to live. 



Trees as a Protective Covering for the Earth. The 

 soil in a forest is of such a nature that it acts like a sponge 

 in absorbing a large amount of water. The soil is held 

 in place by the roots of the trees, while the foliage of the 

 trees prevents the evaporation of water from the soil. 

 When the forests are removed, surface erosion takes place 



Forest Service, Washington, D. C. 



FIG. 298. A Portion of an Old Sale Area Cut too Heavily and Later Badly 

 Windblown. The Timber is Lodgepole Pine, Medicine Bow National Forest, 

 Wyoming. 



much more rapidly (Figure 297). If observations are 

 made while traveling in almost any part of the United 

 States, evidences of such erosion will be seen. Sidehills 

 will be marked with deep gullies made by the surface 

 water as it runs off after rains. Often streams that were 

 never dry when the region was covered with trees 

 remain dry several months in the year after the trees 

 have been removed. 



