If the motor and its appurtenances, and some of the purely auxiliary
planes, be omitted, we have a _glider_. The glider is not a toy; some
of the most important problems of balancing may perhaps be some day
solved by its aid. Any boy may build one and fly therewith, although
a large kite promises greater interest. The cost is trifling, if the
framework is of bamboo and the surfaces are cotton. Areas of glider
surfaces frequently exceed 100 square feet. This amount of surface
is about right for a person of moderate weight if the machine itself
does not weigh over fifty pounds. By running down a slope, sufficient
velocity may be attained to cause ascent; or in a favorable wind (up
the slope) a considerable backward flight may be experienced. Excessive
heights have led to fatal accidents in gliding experiments.
[Illustration: THE WITTEMAN GLIDER]