THE HURRICANE, THE TYPHOON, AND THE TORNADO. 13 
Their courses have been frequently and accurately laid down on 
charts. 
All these storms are of the nature of whirlwinds, and the direc- 
tion and rate of motion of the wind in the hurricane is very dif- 
ferent from the direction and rate of motion of the whole hurri- 
cane. Thus within a very short time, and in the same spot, during 
the late storm, the wind is described to have blown from various 
points of the compass ; and while the whole storm was moving at 
the rate of ten or twenty miles per hour the wind within the storm 
was blowing at the rate of a hundred miles an hour. Almost 
every one must have noticed on a summer day a cloud of dust 
raised from the earth, whirling round leaves and twigs with great 
violence, and advancing with comparative slowness in a certain 
direction. The same, on a vastly larger scale, is the case with 
these terrible hurricanes. They twist round with fearful ra- 
pidity, on a central axis where there is generally a calm, the 
belt of storm moving steadily at the same time along the sur- 
face. Waterspouts at sea, and sandstorms in the deserts of 
Africa, are similar phenomena. 
Originated chiefly because of the excessive heating of the 
earth in some special localities near the equator, and set in mo- 
tion by opposite currents of air rushing in to fill the partial 
vacuum thus formed, it is not extraordinary that the central 
part of a whirlwind should be comparatively calm aud be accom- 
panied by electrical phenomena ; nor need we be surprised at 
the mechanical force exerted where the wind is once set in 
motion. It is recorded that even small whirlwinds lift not 
only vast quantities of dust, but carry even fish into the air. 
The partial vacuum in the central part, where the pressure 
is reduced from 100 to 150 pounds on each square foot of sur- 
face, acts in the most extraordinary manner on buildings, not 
unfrequently forcing the windows and roof outwards, instead 
of blowing them into the building, and sometimes lifting a 
whole house from the foundation. The mere force of the wind 
moving wdth extraordinary rapidity, in a spiral and with a com- 
plicated motion (one motion round the axis, the other in a curved 
line in the main course of the storm), is suflicient to explain 
most of the wonderful things recorded of these phenomena. 
Some that verge on the impossible may, perhaps, owe a little to 
the fears and lively imagination of the describes 
The class of storms to which these great tropical hurricanes 
belong is now generally called cyclonic, from their moving 
round an axis in a circle, or rather spiral. Though producing 
their most striking effects in the tropics, and best known in the 
Tropic of Cancer, they are not limited to such latitudes ; occa- 
sionally crossing the Atlantic into the temperate zones, and 
sometimes originating apparently near our own shores. The 
