The illustration of the fire used above also affords a good example of the way rotation may result from rising air. Any one who has watched a great fire in calm weather knows that sparks and smoke do not rise straight up, but in spirals and whirls, the warmer centers rising faster, just as the middle of a stream flows faster than the edge.
But the powerful winds and the damage done were not all the work of the marginal whirlwinds. A storm center moving so rapidly must necessarily have carried a steady high wind. Leaving Wyoming, by Wednesday evening the storm was in the middle of Colorado; on Wednesday night, it moved well into Kansas; on Thursday, it crossed States of Missouri and Illinois, and Thursday night it was passing over Indiana.
The climax of energy was apparently not attained until the storm reached Illinois. In Missouri, more or less damage was done to fences and buildings, from Sedalia to St. Louis. At the former place, a roof or two was blown off, and the teachers in one of the schools were so alarmed that they dismissed the children. Jefferson City, sixty miles further on, made a record of damaged roofs and shattered windows. At St. Louis, there was a deluge of rain at three o’clock in the afternoon, lasting a half hour; and the wind blew with fury during the evening and greater part of the night. It drove in and smashed some plate-glass windows, blew off an occasional roof, and from the top of the corner of St. Patrick’s School, hurled to the sidewalk a stone weighing, probably, four hundred pounds.
The story of the Louisville tornado serves to well illustrate all the peculiar features of the local whirlwinds produced by great storms. They seldom travel more than thirty miles; usually much less. Sometimes as large as two miles in diameter, they seldom exceed five hundred yards; and one of but fifty yards in diameter may be powerful enough to wreck a house.
Often it is possible to trace the path of a tornado through the forest a century or more after its passage; for the reason that trees once destroyed are usually replaced by different varieties. But the tornado usually originates in the open country, though after its formation it may sweep through heavy timber.
TORNADO FOLLOWED BY RAIN STORM.