First, by means of phials
filled with dew, which would attract and cause to mount up.
Secondly, by a great bird made of wood, the wings of which should
be kept in motion. Thirdly, by rockets, which, going off
successively, would drive up the balloon by the force of
projection. Fourthly, by an octahedron of glass, heated by the
sun, and of which the lower part should be allowed to penetrate
the dense cold air, which, pressing up against the rarefied hot
air, would raise the balloon. Fifthly, by a car of iron and a
ball of magnetised iron, which the aeronaut would keep throwing
up in the air, and which would attract and draw up the balloon.
The wiseacre who invented these modes of flying in the air seems,
some would say, to have been more in want of very strict
confinement on the earth than of the freedom of the skies.
In 1670 Francis Lana constructed the flying-machine shown on the
next page. The specific lightness of heated air and of hydrogen
gas not having yet been discovered, his only idea for making his
globes rise was to take all the air out of them. But even
supposing that the globes were thus rendered light enough to
rise, they must inevitably have collapsed under the atmospheric
pressure.
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