LOCAL STORMS 235 



on a board covered with dark cloth, arranged just outside a 

 window so the flakes could be photographed through the 

 glass. More than 1700 different forms of snow flakes have 

 been photographed by Mr. W. A. Bentley of Jericho, Vt. 



FIG. 166. Types of snow crystals. 



V. LOCAL STORMS 



261. Local Storms; Showers. The showers of summer 

 nearly always develop from cumulus clouds. These showers 

 are one of the most interesting weather features to observe. 

 They sometimes form in an hour or two from a clear sky. 

 Though they usually move eastward, they may come from any 

 point of the compass. They sometimes appear to travel 

 backward or sidewise instead of proceeding forward. Thus, 

 the summer shower often seems to come with little or no warn- 



