on to the square of the velocity.
Thus wind at 10 miles an hour has four times the pressure of wind at
5 miles an hour. The greater this pressure the large and heavier the
object which can be raised. Any boy who has had experience in flying
kites can testify to this, High winds, however, are almost invariably
gusty and uncertain as to direction, and this makes them dangerous for
aviators. It is also a self-evident fact that, beyond a certain stage,
the harder the wind blows the more difficult it is to make headway
against it.

Launching Device for Gliders.

On page 195 will be found a diagram of the various parts of a launcher
for gliders, designed and patented by Mr. Octave Chanute. In describing
this invention in Aeronautics, Mr. Chanute says:

"In practicing, the track, preferably portable, is generally laid in
the direction of the existing wind and the car, preferably a
light platform-car, is placed on the track. The truck carrying
the winding-drum and its motor is placed to windward a suitable
distance--say from two hundred to one thousand feet--and is firmly
blocked or anchored in line with the portable track, which is preferably
80 or 100 feet in length. The flying or gliding machine to be launched
with its operator is placed on the platform-car at the leeward end of
the portable track. The line, which is preferably a flexible combination
wire-and-cord cable, is stretched between the winding-drum on the track
and detachably secured to the flying or gliding machine, preferably by
means of a trip-hoop, or else held in the hand of the operator, so that
the operator may readily detach the same from the flying-machine when
the desired height is attained."

How Glider Is Started.

"Then upon a signal given by the operator the engineer at the motor
puts it into operation, gradually increasing the speed until the line
is wound upon the drum at a maximum speed of, say, thirty miles an
hour. The operator of the flying-machine, whether he stands upright and
carries it on his shoulders, or whether he sits or lies down prone upon
it, adjusts the aeroplane or carrying surfaces so that the wind shall
strike them on the top and press downward instead of upward until the
platform-car under action of the winding-drum and line attains the
required speed.

"When the operator judges that his speed is sufficient, and this depends
upon the velocity of the wind as well as that of the car moving against
the wind, he quickly cause