ores na at as LOTT fe ee, aes ee ae 
156 NATURE [ Dee, 15, 1881 
been thrown outward with great violence, the wreckage 
presenting the appearance of a sudden explosion, proving 
that the pressure outside the building was instantaneously 
and largely diminished, and the building wrecked by the 
expansion of the air within. It is in this way that the 
tornado works no inconsiderable part of its most dreadful 
havoc in the destruction of human life. 
During the storm of 1703, the greatest recorded in 
British history, it was observed that the roofs of many 
| houses on the lee side of the buildings were wrecked as if 
| by an explosion within. The destruction in this case 
| was caused by the extreme rarefaction produced on the 
_ lee side of buildings by the mere mechanical action through 
| friction of the terrific wind which swept past them, The 
records of tornadoes abound in illustrations of houses and 
other structures thus reduced to hopeless wrecks. 
It is probable that the wind sometimes reaches a force 
in tornadoes exceeding what is ever reached in cyclones. 
During the tornado which occurred in Ohio on February 
4, 1842, large buildings were lifted entire from their foun- 
dations, carried several rods through the air, and then 
and gilded ball of the Methodist Church were carried 
fifteen miles to the north-eastward. On this incident 
Prof. Ferrel remarks that the ascending currents which 
could keep this structure suspended in the air for at least 
fifteen or twenty minutes must have had an enormous 
velocity. 
The usual position of the gyrating columns of whirl- 
dashed to pieces, some of the fragments being transported 
a distance of seven or eight miles; and large oaks nearly 
seven feet in girth were snapped across like reeds. This 
tornado sped on its course at the rate of thirty-four miles 
an hour, and at one place it did its fearful work in the 
brief space of a minute. During the tornado which swept 
over Mount Carmel, Illinois, June 4, 1877, the spire, vane, 
Among other posi- 
winds is vertical, as seen in Fig. 1. 
tions the columnassumes a slanting direction as in Fig. 2, 
and a curved form as in Fig. 3. It is probable that to 
these latter forms many of those stationary or slowly 
moving dangerous squalls are to be referred that spring 
up with unexpected suddenness so frequently in such 
regions as the western lochs and islands of Scotland— 
