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If you turn a bottle upside down, and, while in that position, send a cork-screw up into the cork, you set in motion the same force which is applied in the spiralifer. As the screw screws itself up into the cork, so the spiralifer screws itself up into the air.
We are in turn about to make it serve us as a slave, just as the water on which we launch the ship, as the solid earth on which we press the wheel!" There is a toy called the spiralifer, which is common enough in towns, and which is, doubtless, known to almost every one. It consists of four flat fans attached to a spindle somewhat after the manner of the arms of a windmill.
Air is the resisting medium in the case of the mill; water and cork respectively in the other cases. The only difference between the windmill and the spiralifer is, that the first is moved by the air pressing against it, the other by itself, in its rotatory action, pressing against the air.
The screw-propeller of a ship is just a spiralifer placed horizontally, acting on water instead of air, and having a vessel placed in front of it. Now, Monsieur Nadar's aerial locomotive is a huge spiralifer, made strong enough to carry up a steam-engine which shall keep it perpetually spinning, and, therefore, perpetually ascending.
It is placed in a hollow tube and made to spin violently by pulling a string wound round the spindle. The result is that the spiralifer leaps out of the hollow tube and ascends powerfully as long as the violent spinning motion continues.
Of course the screw remains sticking there when the motive power ceases, because of the density of the medium through which it moves, while the spiralifer, when at rest, sinks, because of the fluidity of the air; but the principle of motion in each is the same.
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