One of the first difficulties which the novice will
encounter is the uncertainty of the wind currents. With a
low velocity the wind, some distance away from the
ground, is ordinarily steady. As the velocity increases,
however, the wind generally becomes gusty and fitful
in its action. This, it should be remembered, does not
refer to the velocity of the machine, but to that of the
air itself.
In this connection Mr. Arthur T. Atherholt, president
of the Aero Club of Pennsylvania, in addressing the
Boston Society of Scientific Research, said:
"Probably the whirlpools of Niagara contain no more
erratic currents than the strata of air which is now immediately
above us, a fact hard to realize on account
of its invisibility."
