as aboard, realised the
extreme danger of the envelope bursting as the balloon ascended, and at
16,000 feet he thrust a staff through the envelope--another account says
that he slit it with his sword--and thus prevented disaster. The descent
after this rip in the fabric was swift, but the passengers got off
without injury in the landing.

Meusnier, experimenting in various ways, experimented with regard to
the resistance offered by various shapes to the air, and found that an
elliptical shape was best; he proposed to make the car boat--shaped, in
order further to decrease the resistance, and he advocated an entirely
rigid connection between the car and the body of the balloon, as
indispensable to a dirigible.[*] He suggested using three propellers,
which were to be driven by hand by means of pulleys, and calculated that
a crew of eighty would be required to furnish sufficient motive power.
Horizontal fins were to be used to assure stability, and Meusnier
thoroughly investigated the pressures exerted by gases, in order to
ascertain the stresses to which the envelope would be subjected. More
important still, he went into detail with regard to the use of air bags,
in order to retain the shape of the balloon under varying pressures of
gas due to expansion and consequent losses; he proposed two separate
envelopes, the inner one containing gas, and the space between it and
the outer one being filled with air. Further, by compressing the air
inside the air bag, the rate of ascent or descent could be regulated.
Lebaudy, acting on this principle, found it possible to pump air at the
rate of 35 cubic feet per second, thus making good loss of ballast which
had to be thrown overboard.

[*] Hildebrandt.

Meusnier's balloon, of course, was never constructed, but his ideas have
been of value to aerostation up to the present time. His career ended
in the revolutionary army in 1793, when he was killed in the fighting
before Mayence, and the King of Prussia ordered all firing to cease
until Meusnier had been buried. No other genius came forward to carry
on his work, and it was realised that human muscle could not drive a
balloon with certainty through the air; experiment in this direction
was abandoned for nearly sixty years, until in 1852 Giffard brought the
first practicable power-driven dirigible to being.

Giffard, inventor of the steam injector, had already made balloon
ascents when he turned to aeronautical propulsion, and cons