Abstract
I. WHILE identical with and resembling cyclones in not a few of their leading characteristics, tornadoes and whirlwinds are yet in several all-important respects widely and radically different. The largest tornadoes are of so small dimensions when compared with the smallest cyclones as to point to a difference so decided that admits of no shading of the one class of phenomena into the other. Again, cyclones occur at all hours of the day, whereas whirlwinds and tornadoes are all but restricted to the warmer hours of the day, and perhaps altogether to the time of the day when the sun is above the horizon. Further, and intimately connected with the above, cyclones take place under conditions which imply unequal densities at the same heights of the atmosphere, whether these be due to inequalities in the geographical distribution of temperature or humidity; but whirlwinds occur where the air is unusually warm or moist for the time, and where, consequently, temperature and humidity diminish with height at an abnormally rapid rate. To put it otherwise, cyclones are phenomena consequent on a disturbance of the equilibrium of the atmosphere considered horizontally, but tornadoes, on the other hand, have their origin in a vertical disturbance of atmospheric equilibrium.
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Tornadoes, Whirlwinds, Waterspouts, and Hailstorms . Nature 25, 155–157 (1881). https://doi.org/10.1038/025155a0
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DOI: https://doi.org/10.1038/025155a0