LOCAL STORMS 



247 



and plank through sheets of steel. The tornado is confined 

 principally to the United States east of the Rocky Mountains, 

 and rarely occurs in other portions of the earth. Most torna- 

 does develop in the southeast half of a low-pressure area. 



FIG. 177. Effects of a tornado. 



FIG. 178. Effect of tornado; straws driven into wood. 



NOTE. The name "cyclone" belongs to a wholly different class of 

 storms (see Arts. 284 and 302) and should never be used for a tornado. 

 (1) The tornado always has the local twisting winds and a hanging core 

 of revolving cloud; the cyclone never has either. (2) The diameter 

 of the tornado is always a few hundred yards, or less; the diameter of 

 the cyclone is always a few hundred miles or more. 



