208 THE WORK OF RUNNING WATER 



and forced to high levels. If the water is liable to con- 

 tamination, expensive processes of purification and clarifi- 

 cation are installed in the interest of public health. 



QUESTIONS 



Trace the probable journey of the water that fell near your 

 home during the last heavy rain until it reached its journey's end. 



Describe some of the effects of running water that you have 

 seen. 



Give the history of a river's development in a moist climate. 



How do rivers in dry climates differ from those in moist climates ? 



Describe some of the accidents that are liable to happen during 

 a river's development. 



How have rivers affected history? 



What has been man's part in the development of waterways? 



What becomes of the water which sinks into the ground ? 



How is water supplied to the cities and towns near your home? 



Why is a pure water supply so important ? 



