TORNADOES. 157 



tremes that have been ventured upon and of course are not reliable, while in the 

 majority of instances more trustworthy determinations have ranged between loo 

 and 500 miles per hour. 



The uncertainty arising on this point of ascertaining the velocity of centri- 

 petal currents, depends upon or is rather an outcome of the difficulty attending 

 the acquirement of the requisite (absolutely) reliable data. In all carefully 

 conducted investigations heretofore made, there has unfortunately occurred such 

 a long interval between the happening of the storm and the arrival of the person 

 authorized to commence the work, that valuable and satisfactory results in this 

 direction were precluded. It is always of prime importance to ascertain definite- 

 ly, what portion of a building or other object was first struck by the wind in order 

 to determine the configuration and inclination of the exposed surface. As a rule 

 such examination is rendered next to impossible by the rapidity with which de- 

 vastated districts recover from the violence of the storm. This statement is a 

 most praiseworthy and well deserved commentary on the exemplary industry and 

 determined spirit of the people of the Lower Missouri Valley. With the gyratory 

 motion of the tornado cloud, objects are drawn inward to the centre of the storm 

 and then carried violently upward by a spirally inward and upward motion 

 which fairly crushes and grinds into pieces buildings, trees and whatever else falls 

 in the line of the advancing cloud. The spirally upward motion throws the as- 

 cending debris in a circular manner, outward at the top of the tornado cloud. 

 This debris when beyond the central whirl of the cloud, falls to the earth, but in 

 such a manner and so disposed as to indicate the character of the force which 

 acted upon it. 



No. II. is called the progressive motion of the tornado cloud, the motion 

 which determines the cloud's progress from one point to another. The rate of 

 progressive velocity ranks next in order to the velocity of motion No. I. 

 although it is certainly at all times far below the high degree of the latter. 



The rate of progress of the tornado cloud is subject to great variability 

 throughout the path of any one storm, although on the average tornado clouds 

 possess a moderately uniform velocity of progression. Some observers have in- 

 dicated the movement by the following expressions : "All in an instant." "Gone 

 in a moment." "Quicker than thought." "Without a moment's warning." "It 

 moved no faster than a horse gently galloping." "I just saw what it was, and then 

 all was over." "Before I had time to turn about in my tracks it flashed by me." 

 "It seemed to remain almost motionless, as if held to the ground by some myste- 

 rious force;" "I shuddered, held my breath, and the monster had vanished." "It 

 seemed to move no faster than I could run." 



These estimations of velocity are not to be taken altogether literally. The 

 circumstances under which the impressions were received must be considered, 

 viz : undue excitement or abject terror. However, the comparative results are 

 important, and to a certain extent reliable. Through them, you will at least not 

 be led astray in your conceptions of the awful grandeur of the panorama, or fall 



