620 Tornadoes of Kansas and Missouri . [September, 
or less areas of the earth’s surface by solar heat every day. 
The vapour contained in the air is thus carried up by the 
ascending current until it is condensed into cloud by the ex- 
pansion and cooling of the air which contains it. The latent 
heat of the vapour thus liberated tends to elevate the tem- 
perature of the air containing it, causing it to be lifted to 
still higher altitudes. The violence of this upward move- 
ment is largely due to the amount of vapour, or the “ steam 
power of the air.” 
The centre, or core, of a storm sometimes becomes a tor- 
nado, which possesses a linear or gyratory movement. Con- 
nected with these there is a swaying movement, caused by 
obstacles, such as hills and forests, along the path of the 
storm, and sometimes the tornado seems to be drawn up into 
the air. 
I have noticed quite a number of whirlwinds observing 
the laws of tornadoes. In 1872 I saw a beautiful whirlwind 
at Burlington, Kansas. While walking toward the town 
from the north-west, I heard a rushing sound south- 
west of me. Soon I saw the prairie grass swaying violently, 
and I had a perfect view of a miniature tornado, as it passed 
across the road a few rods ahead of me. The atmosphere 
was tranquil at the time. Here was a whirlwind ploughing 
its way through a tranquil atmosphere at the rate of ten 
miles an hour, moving east by twenty degrees north, and 
gyrating in a direction contrary to the hands of a watch. 
Tornadoes in the northern hemisphere are translated 
toward the east by about twenty degrees north. Deflections 
from this direction are supposed to be occasioned by local 
causes, such as rivers, surface currents, &c. The Irving 
tornado was deflected from its path near Frankfort, passing 
up the west fork of the Vermillion river, in a north and 
north-east direction, a distance of fifteen miles, when it again 
resumed its normal path. North of the equator, tornadoes 
revolve in a direction contrary to the sun, or the hands of a 
watch with its face upward, while south of the equator they 
revolve in an opposite direction. 
Tornadoes, according to this theory, originate in disturb- 
ing causes aCting suddenly, but take their character from 
the cosmical conditions of the globe. The average tempe- 
rature of the globe is about 85° at the equator, decreasing to 
about zero at the poles. This excess of heat expands the 
air in the equatorial regions, which flows over toward each 
pole. The larger portion of this circulation, however, is 
confined to a belt not extending beyond the thirtieth parallel 
of latitude, because the current is cooled in the upper 
regions, and the meridians narrow toward the poles. 
