134 The Sky 
level, and should an upward convection current be present ; 
at the same time, the entire vertical column of air may be © 
drawn into a violent whirlwind. As the inner core of the ~ 
whirlwind is expanded by centrifugal force it is cooled some- 
what, and a funnel shaped cloud spout may form within — 
the vortex. Eventually the spout may reach down to the | 
spray whipped up from the surface of the sea by the wind. — 
The waterspout makes a deafening roar and though it ap-§ t 
pears to draw water up from the sea, actually the water it | 
contains is fresh water condensed from the atmosphere. The | : 
average speed of a waterspout is about 25 miles an hour, but 4 
the winds of which it is composed reach the highest wind © 
velocities known, up to 500 miles per hour. A good sized _ ! 
waterspout is a real enough danger, capable of tearing to 
pieces anything which might come into its path. { 
