98 NATURE STUDY' BY GRADES 



school. Watch the changes . in any of these conditions. 

 Usually a south wind, changing to the northwest, will be 

 followed by a storm in the inter-mountain region. In other 

 localities indications of storms are somewhat fixed or regu- 

 lar. Set out a rain gauge, or other vessel, to catch and 

 measure the precipitation. 



Let the pupils watch the falling snowflakes, and examine 

 them with lenses. Call attention to the needle-like crystals 

 of which they are composed. Compare them with the first 

 crystals of ice that form on the surface of freezing 

 water. 



Discuss other forms of precipitation, rain and hail. 

 Under what conditions do they form ? Where does the snow 

 usually fall more heavily, in the mountains or the valleys? 

 Why? Discuss the benefits of a heavy snowfall in the 

 mountains, in the arid regions, and its influence upon irriga- 

 tion, and consequent value to the farmer. 



Do the snows that fall in the mountains in the winter 

 affect in any way the farmers in the great river basins? 

 What causes high waters in the spring? What conditions 

 bring about floods in the river basins ? How may floods be 

 predicted? Can man influence floods in any degree? 

 How? 



Consider, also, the influence of summer rains, in various 

 regions. 



After the storm, melt the snow that fell in the rain gauge 

 and determine how many inches of snow it takes to make 

 one inch of water. 



Since the heaviest precipitations in the arid regions of the 

 United States occur nearest the high mountains, the level 

 lands are mostly deserts, and the largest cities and farms 

 are among the mountains. 



