CHAPTER IV 

 EFFECTS OF THE MOVEMENTS OF WATER 



You have seen that water is a great tool of nature, and 

 that heat and the force of gravity are the forces that work 

 with this tool. Air is another great tool of nature, and it, 

 too, is moved by heat and by the force of gravity. Up and 

 down, across the surface of the land and under it, these 

 tools keep moving and working. The winds keep blowing, 

 rains keep falling, and water keeps running back to the 

 sea. What effects do these things have upon us? 



As air and water move they move other things with 

 them. Things that are loose are shifted about. High 

 winds blow dust and sand from place to place, and high 

 water sweeps along everything in its path that is not firmly 

 anchored. Thus some shifting of the materials of the 

 earth's surface goes on all the time, and running water is 

 by far the most important of the shifters of materials. 

 Water is eighty times as heavy as air; so it can carry eighty 

 times as much. Every muddy stream is carrying a load 

 that will be laid down again somewhere. This is called 

 the wash or the waste of the land. The Mississippi River 

 carries out to sea a million tons of mud and sand each day. 

 (How many freight-trains of fifty cars each would be re- 

 quired to carry this load, allowing five tons to the car?) 



Running water plays an important part in the lives of 

 men. It does both good and harm. The rivers carry 

 away to the sea much good fertile soil, but they also bring 

 good soil down from the hills and spread it along their 



