184 -A YEAR IN SCIENCE 



the present time, in the United States, about 26,000,000 

 horse power is developed from coal and about 

 5,500,000 horse power from water. The amount of 

 water power capable of being developed by the streams 

 of the country depends upon the condition of the 

 rivers, whether they be at low or 'high water stage. 

 It is estimated that the streams in their low water 

 stage will fur-nish almost 40,000,000 horse power. This 

 is much more than the total amount generated now, 

 but the demands for power will increase as the 

 country grows. 



Questions 



1. In what ways is the rain which falls upon the 

 ground disposed of? 



2. Upon what conditions does the erosive power 

 of a stream depend? 



3. How much sediment has it been estimated that 

 the Mississippi Kiver carries into the Gulf of Mexico 

 every day? 



4. Why is this considered a great loss to the 

 country ? 



5. Suggest practical methods for preventing soil 

 erosion. 



6. Describe fully the stages through which a river 

 passes in its development from youth to old age. 



7. If possible, name and locate rivers which are 

 examples of these different stages. 



8. How do you account for the fact that Niagara 

 Falls is receding? 



