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tornadoes. Newspapers have made us so familiar with these that 
we need not dwell long on their nature. They develop, always, 
S.E. of a centre of low barometer, and generally, 200 miles or 
more distant, where volumes of moist, warm air are attracted 
northwards from the Grulf of Mexico. Their course is towards 
E.N.E., in tracks rarely over a few thousand feet wide and 
generally only a few miles in length, hut almost everything 
is swept before them. Other tornadoes often follow at regular 
intervals of time and distance. That at Louisville, Kentucky, 
on March 28th, 1890, the most destructive since Orinnell, Iowa, 
was visited in 1882, was one of eighteen such, “ besides violent 
storms of hail and straight winds.” 76 lives were lost, although 
12 hours’ warning had been sent to the district. The roar was 
like a thousand trains on bridges.” 
The points of resemblance, however, are so many as 
practically to give a summary of the whole phenomenon. 
We have:— 
(1) The meeting of two clouds to the S.W. by W. 
(2) A sudden darkening. 
(3) The overpowering roar. 
(4) The association with a thunderstorm. 
(5) The thunder and lightning accompanying the rush.” 
(6) The position in the S.E. octant of the depression. 
(7) The centre was 300 miles distant.* 
(8) The “ Tornado season” runs from March to September. 
(9) They begin “just after the hottest part of the day.” 
(10) The destruction at Heckington, 70 miles S.E. of York, 
of the windmill, about 1| hours later.* 
(11) The definite and narrow limits of width. 
(12) The direction, W.S.W. to E.N.E. (more S.W. to N E. 
in tornadoes). 
(13) The chief damage along the S. border. 
(14) The rapidity of transit. 
(15) The absence of any conclusive proof of a true whirl at 
the earth’s surface. 
* Compare these with Prof. Hazen’s summary {^Science, XV., p. 270), where 
it says :—‘ an hour or so later, another line ♦ * * about 50 miles S.E. of 
the first,’ which itself develops ‘ 200 to 400 miles to the S.E. of the centre of the 
general storm.’ 
