airships. Government officials and many others turned their attention
to the work. Factories were put in operation in several countries of
Europe and by the year 1905 the dirigible had been fairly well
established. Zeppelin, Parseval, Lebaudy, Baidwin and Gross were
crowding one another for honors. All had given good results, Zeppelin
especially had performed some remarkable feats with his machines.

In the construction of the dirigible balloon great care must be taken
to build a strong, as well as light framework and to suspend the car
from it so that the weight will be equally distributed, and above all,
so to contrive the gas contained that under no circumstances can it
become tilted. There is great danger in the event of tilting that some
of the stays suspending the car may snap and the construction fall to
pieces in the air.

In deciding upon the shape of a dirigible balloon the chief
consideration is to secure an end surface which presents the least
possible resistance to the air and also to secure stability and
equilibrium. Of course the motor, fuel and propellers are other
considerations of vital importance.

The first experimenter on the size of wing surface necessary to sustain
a man in the air, calculated from the proportion of weight and wing
surface in birds, was Karl Meerwein of Baden. He calculated that a man
weighing 200 lbs. would require 128 square feet. In 1781 he made a
spindle-shaped apparatus presenting such a surface to the resistance
of the air. It was collapsible on the middle and here the operator was
fastened and lay horizontally with his face towards the earth working
the collapsible wings by means of a transverse rod. It was not a
success.