150 



stones range in size from peas up to walnuts and in 

 some cases have been known to reach the size of hen's 

 eggs. The main theory of hail is considered the rotary 

 motion of the wind as in a cyclone, excepting it is hor- 

 izontal instead of vertical. Two layers of clouds 

 usually exist, one of rain the other of snow. The 

 snow-flakes are supposed to be caught in the whorl and 

 rapidly dipped in succession into water and then snow, 

 receiving alternate coatings of each, until at last they 

 are hurled to the ground. There are other theories 

 presented but the above is usually accepted as correct. 

 When the temperature of the condensed moisture is 

 below 32^ F. snow falls providing the conditions per- 

 mit a definite crystallization. The snow-flakes present 

 many beautiful forms, but are all composed of minute 

 rhombohedrons of ice. The star-shaped are the most 

 common. If the temperature at the surface be much 

 Avarmer than 32^ any snow that is formed in the upper 

 regions must melt before it reaches the ground, hence 

 in the temperate zones the snow falls occur in winter 

 only and in the tropics it never falls except near the 

 summit of high mountains. At a certain height above 

 the sea according to latitude and physical changes, the 

 ground is permanently covered with snow. 



Glaciers are large rivers of ice usually found in 

 mountainous regions,which move very slowly and make 

 their way down the ravines and chasms. Like rivers 

 they have their tributaries. They are usually white but 

 when mixed mth sand and debris become quite dark. 

 These glaciers are sometimes very smooth while others 

 are rough and jagged. These glaciers are very power- 

 ful carrying everything with which they come in con- 



