98 CALIFORNIA ACADEMY OF SCIENCES. 



cylindrical film of sand having a diameter of approximately 

 twenty feet, moving slowly upon its direct coarse and with 

 a velocity of about ten feet per second around its central 

 axis. In and upon this moving circle were six small revolv- 

 ing circles not exceeding one foot in diameter and having a 

 greater velocity, probably inversely proportionate to their 

 diameters. Their greater velocity enabled them to take up 

 from the surface of the ground more sand and debris than the 

 larger circle, and as a consequence, they maintained strong 

 and independent columns upon the larger but weaker one. 



The movement, which was from right to left in its circu- 

 lar projection, passed within a few rods of me. Approach- 

 ing, it was upon ground having a loose sandy surface and 

 free from obstructions. Near me the ground presented a 

 few scattered shrubs with sand intervening; beyond, there 

 was open sand again, then a street with a line of buildings 

 upon one side; beyond the buildings were: first, sand, then 

 sand and shrubs. The fourth movement was strongly de- 

 fined when I first noticed the general movement, and so 

 continued during the time I was able to observe it. When 

 the movement reached the ground covered with shrubs and 

 one of the smaller movements encountered them, it would 

 apparently become obliterated, but directly it would appear 

 in its place again, simply having been broken at its earth 

 contact. The movement passed directly over the buildings 

 noted and again made ground contact, maintaining its sev- 

 eral movements, which were sustained while it was within 

 my observation. 



In the recorded observations of devastation effected by 

 tornadoes, we find instanced the twisting of branches of 

 trees about their trunks, the turning of chimneys upon their 

 bases without being thrown dow^n, the whirling of objects 

 in the air, the erratic movement of bodies, etc., none of 

 which are explainable by either or all of the movements 

 heretofore recognized, but which are readily accounted for 

 by this fourth movement. 



