158 KANSAS CITY REVIEW OF SCIENCE. 



into the fatal mistake of encouraging a belief that the tornado is not what the 

 united experience of all observers has portrayed it. 



This data will not answer however, to figure on very closely, but the factors, 

 average diameter of cloud, actual time (local or standard) and measured dis- 

 tances, must be carefully obtained before an approach to accurate calculations 

 can be secured. Reliable data are very difficult to obtain, especially time. This 

 fact should be thoroughly appreciated by observers and every reasonable effort 

 made by them to examine their clocks or watches upon the approach and passage 

 of the tornado cloud. Generally speaking, it is a good habit to form, of jotting 

 down in some place of ready reference the hour, day, month and year of notable 

 events. 



In regard to this matter of time, so far as past determinations can be 

 valued, the progressive velocity of the tornado cloud is variously estimated at 

 from twenty-five to seventy miles per hour. The former is perhaps too low and 

 the latter quite likely too high, and although in both instances they represent the 

 extremes, yet either of the above velocities may have existed for short intervals. 

 The true average is probably about forty miles per hour. 



No. III. is termed the rising and falling motion of the tornado cloud, the 

 character of which finds definition in the following expressions from various wit- 

 nesses : "The top of the cloud seemed to pop up and down, and then to rush 

 forward." "It bounded over the ground like a ball." "It was the strangest 

 jumping and flopping object I ever saw." "At times it seemed to lash the earth 

 in terrific fury with its huge tail." "It came along, popping up and down in a 

 most fantastic way." "Rising up like the uncoiling of a huge rope, it cut loose 

 from the earth and passed over us with a horribly whizzing sound." "Ever and 

 anon it would shoot directly upward from the earth, sometimes with great rapidity, 

 and then again quite slowly, each time dashing to the surface with apparently 

 renewed vigor.'' 



It is perhaps clearly, seen that this a distinct motion with striking pe- 

 culiarities which define its character. Sometimes, upon the lifting of the tor- 

 nado cloud from the earth, it does not again descend for a distance of sever- 

 al miles, at times making the return movement or descension twenty or thirty 

 miles distant, the intervening space proving a complete blank in its track. 

 More frequently, however, these gaps are from one to five miles in length. 



While the tornado cloud is traversing the atmosphere at some considerable dis- 

 tance above the earth, it may reach down so low as to just skim over the tops of 

 the highest trees ; descend to a level with the roofs of buildings, simply scaling 

 off the shingles in spots or entirely on one side, leaving the roof-boards and 

 rafters unmoved; removing the tops of chimneys; taking out all the fans in the 

 wheel of a wind-mill and leaving every portion (even the tail) of the remainder of 

 the mill unharmed ; take off the cornice without disturbing the remainder of 

 the roof; removing simply the top board of a five-board fence, or one or two 

 of the top rails of an ordinary rail fence. 



