214 FIRST YEAR COURSE IN GENERAL SCIENCE 



fallen rain must run off. Excessive rainfall may produce 

 floods even in forested regions; it will surely do so in de- 

 forested regions. 



China suffers greatly from floods. Its forests long ago 

 disappeared, as every inch of land was needed to produce 

 food for the dense population. In southern California floods 

 from the deforested San Bernardino Mountains have cov- 

 ered fertile lands with sand and gravel. Later, in the dry 

 season, when water is needed for irrigation, there is none 

 in the beds of the streams, because the water was not held 

 back by the trees nor absorbed by the spongy forest floor. 



236. The National Importance of Forests. Young 

 forests are sometimes destroyed by fire or by grazing. Denu- 

 dation follows, and the soil, from which a new forest might 

 have grown, is carried away to the sea. Correction of dam- 

 age done by floods has already cost France thirty-five 

 million dollars and the task is still unfinished. These floods 

 resulted from the destruction of forests by the grazing of 

 sheep. 



The prosperity of a nation depends upon its ability to 

 provide food, water, and fuel for its people. Soil, rivers, 

 and forests are necessary to this provision. There is no more 

 important duty of the government than to guard with care 

 and to develop the sources of its prosperity. 



EXERCISES 



1. How early in the history of a mountain or a continent does 

 degradation begin? 



2. Explain what is meant by the statement that "gravity assists 

 in degradation." 



3. Why is the work of frost more rapid in mountains than in plains? 



4. What is the appearance of young mountains? Why? 

 6. Why is the air purer on mountains than on lowlands? 



6. Tell why there are desert regions north of the Himalayas. 



7. How long must the track of a railroad be, in order to reach an 

 elevation of \\ miles at a uniform 4% grade (a rise of 4 ft. in 100 ft. 

 of track)? 



