114 FIRST YEAR COURSE IN GENERAL SCIENCE 



gion of lower pressure. This disturbance of the atmosphere 

 is often accompanied by a precipitation of rain or snow. As 

 the rain inconveniences us more than does the wind, we often 

 make the mistake of thinking that the precipitation alone 

 constitutes the storm. 



If an atmospheric disturbance prevails over a large area, 

 the storm is said to be general. Such storms are cyclonic 



FIG. 55. AFTER A TORNADO, OMAHA, NEBRASKA 



That the wind had a whirling instead of a direct motion is shown by 

 the position of the beams of this house with respect to the foundation. 

 The house was lifted away from its foundation and turned, before it dropped 

 back. 



storms. As the whirl moves, the wind may change in di- 

 rection and velocity and the amount of precipitation may 

 vary at different places, but the same general conditions 

 continue for hours or even days and then pass away. In 

 the eastern part of the United States cyclonic storms travel 

 generally in a northeast direction. Reports to the Weather 



