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
causes the front of the flying-machine to tip upward, so
that the relative wind striking on the under side of the
planes or carrying surfaces shall lift the flying machine
into the air. It then ascends like a kite to such height
as may be desired by the operator, who then trips the
hook and releases the line from the machine.

What the Operator Does.

"The operator being now free in the air has a certain
initial velocity imparted by the winding-drum and line
and also a potential energy corresponding to his height
above the ground. If the flying or gliding machine is
provided with a motor, he can utilize that in his further
flight, and if it is a simple gliding machine without
motor he can make a descending flight through the air
to such distance as corresponds to the velocity acquired
and the height gained, steering meanwhile by the devices
provided for that purpose.