^98 Tornado in N. E. part of Ohio, Feb. 4, 1842. 

 Tornadoes in the 



From the preceding table it may be inferred, 1. That no sea- 

 son of the year is exempt from tornadoes, but that they occur 

 most frequently in May and June. 2. That they occur chiefly 

 between noon and sunset. Only three out of fourteen occurred 

 during the night ; and 3. That the temperature at the time is 

 unusually elevated. This is a generalization of considerable im- 

 portance, that tornadoes are to be expected only at high tempera- 

 tures, and if they occur in cold months, the temperature is unu- 

 sually high for the season. 4. They are invariably accompanied 

 by lightning and rain, and frequently by hail. 5. Their progress 

 in this country is invariably eastwardly, the mean being about 

 twelve degrees north of east. 6. Their average breadth is about 

 one hundred and twenty rods; length fifteen miles; velocity of 

 progress when violent about thirty miles per hour ; duration of de- 

 structive violence forty five seconds. The duration of destructive 

 violence may be computed from the breadth and velocity of the 

 tornado, on the supposition that its base is circular ; and probably 

 this result is more to be depended upon than the estimates of ob- 

 servers, which are generally made under the influence of fear and 

 likely to be exaggerated. 7. Light objects are frequently trans- 

 ported by the wind a distance of from three to twenty miles. 

 8. Very few human lives are lost by tornadoes. With the excep- 

 tion of the Natchez tornado, the average is but about one to a tor- 



