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THE POPULAR SCIENCE MONTHLY 



JOOM'rra 2UO 



the level corresponding to the base of the cloud. Fixing attention upon 

 any one of these tubes, as the first or outer one, the theory indicates that 

 a particle of air which is lying on that tube in the lowest level continues 

 throughout its motion to follow the same tube. This particle rotates 

 in a spiral about a central axis gradually rising from the ocean towards 

 the cloud, and, rotating in larger and larger spirals, at last it flows out 



from the axis parallel to the surface 

 of the cloud itself. On this outer 

 tube the particle at the sea is moved 

 with a velocity of 22 meters per 

 second and gradually rises upwards 

 and changes its velocity through 

 20, 18, 15, 12, 7, 5, 2 meters per 

 second quite near the surface of the 

 cloud, and finally the velocity falls 

 to zero. At the sea level the velocity 

 is in a circular direction around the 

 axis ; at the cloud level it is moving 

 in a radial direction directly away 

 from the axis. On the outer tube 

 having a large radius the velocities 

 as already given are small, but on 

 the same levels on tube No. 5 quite 

 near the axis the velocities on the 

 same levels become, respectively, 

 182, 159, 136, 110, 80, 44, 31, 14 

 meters per second near the cloud 

 level, and they finally run out to 

 zero. With such enormous veloci- 

 ties as 182 meters per second at the 

 sea level, the causes of the turmoil 

 and destructive effects which are 

 always found in the case of waterspouts and tornadoes passing over the 

 land are readily appreciated. Illustrations of the destructive effects of 

 tornadoes are commonly accessible. The purpose of such a vortex is to 

 lift a mass of air, as in a suction pump, from the surface of the ocean 

 to the cloud, and in this case it is computed that 2,468 cubic meters of 

 air are lifted in each second through each section of this vortex tube. 

 These natural lifting pumps are evidently of great efficiency. 



The dumbbell-shaped vortex operates on substantially the same prin- 

 ciples, though the details are different. In this vortex the air begins 

 at the sea level to flow inwards towards the axis in a spiral which con- 

 tracts up to about 500 or 600 meters above the surface of the sea, and 

 then it begins to expand as in the funnel-shaped vortex. The dumbbell- 



Fig. 2. Dumbbell-shaped Vortex. 



