CIRCULATION OF THE ATMOSPHERE 



45* 



shaped vortex is really composed of two funnel-shaped vortices, the 

 lower one pointing upward and the upper one pointing downward, 

 meeting half way between the two planes of reference. This vortex is 

 really a more efficient lifting pump than the other one just described, 

 and it is found that 16,452 cubic meters of air are moved upwards 

 through each tube per second, so that the dumbbell-shaped vortex is 

 carrying 6.7 times as much air upward as the funnel-shaped vortex. 

 A careful examination of this dumbbell-shaped vortex at Cottage City 

 shows that the lowest sections are not fully developed. The outward 

 curvature of the tube is plainly shown on the picture, but at sea level it 

 is cut off or truncated by the friction of the tube against the water of 

 the ocean. The cutting off of these vortices at some section above their 

 theoretical lowest plane seems to play an important part in practical 

 meteorology. 



On May 27, 1896, a violent tornado of large dimensions passed over 

 the city of St. Louis, causing great destruction in Lafayette Park and 

 thence to the bridge over the Mississippi Eiver. The enormous 

 power of the forces which accompanied this vortex is shown on many 

 pictures which were secured at that time. Large trees were twisted off 



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Fig. 3. Truncated Dumbbell-shaped Voetex. 



and stripped of their branches ; buildings were overturned and destroyed 

 in every conceivable way; heavy iron girders and stone work of the 

 bridge were destroyed; and in short almost limitless powers seem to 

 have been at the disposal of this great vortex. Fig. 3 shows a section 

 of this vortex, the relative distance apart of the tubes, and the part 

 which has been cut off or truncated at about one third of the distance 

 from its lower plane of reference, several hundred meters below the 

 surface of the ground. It has been shown that this St. Louis tornado 

 was about 47 times as efficient as the large Cottage City waterspout in 

 its lifting power, and that at the surface of the ground it developed 

 somewhere between 150 and 250 meters per second; that is, 340 to 560 

 miles per hour. While it is not probable that these enormous theoret- 



