THE CLIMATOLOGY OF THE UNITED STATES. 23 



at any time of the year, but are mostly confined to the 

 summer months and are most frequent in June in the lat- 

 ter part of the afternoon. 



The path of great destruction varies from 300 or 400 

 feet to a quarter of a mile in width, and the course of 

 the tornado ranges from a few miles to 100 or 200 miles. 

 When one occurs in the daytime it can be seen on the 

 western plains a long distance away and its roar can be 

 heard in time for the inhabitants in its path to escape. 

 When it is seen approaching from the southwest a flight 

 to the southeast will soon take one beyond the limits of 

 its devastating path ; but when one occurs at night the 

 inhabitants either awake to find it already upon them or 

 are often so terrified as to lose their self-possession and 

 judgment, and thus lose the opportunity for escape to a 

 place of comparative safety. For this reason, it is common 

 to have " dug-outs " in the ground connecting with the 

 cellar or close at hand, to which a family m:iy quickly re- 

 sort in case of danger. The Signal Service has enlisted 

 the cooperation of town officers, postmasters and others 

 in the regions liable to these visitations, and these parties 

 act practically as voluntary assistants to the regular sig- 

 nal office observers in different parts of the country in 

 collecting information and statistics in regard to every tor- 

 nado visiting their locality. 



After a tornado has occurred, the United States' ob- 

 server at the nearest station will often make a series of 

 personal observations, going over the course of the stonn 

 and taking the observations and accounts of eye-witnesses, 

 and combining them with his own observations make out 

 a report which is forwarded to Washington. In this way 

 much valuable information is obtained and the Signal Ser- 

 vice has been enabled to give within the last year or so 

 indications of the probable occurrence of tornadoes in 



