. It consists of four
flat fans attached to a spindle somewhat after the manner of the arms of
a windmill. 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. If properly constructed, this
toy acts with great force and certainty, and if the spinning motion
could only be kept up, by any means, the ascent would be continued. The
principal here involved is precisely the same as that which causes a
windmill to turn, a screw-propeller to drive a ship, and a cork-screw to
enter a cork. It is pressure against a resisting medium. 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.
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. 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. 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. Perhaps we should have
said that his locomotive is a huge machine to which several spiralifers
are attached, so that while one set raises or (by reversing the engine)
depresses it, other sets drive it sideways. The theory is perfect, and
the practice has been successfully attempted in models. Messieurs
Ponton d'Amecourt and de la Laudelle, we are told--"the one a man of the
world, and the other a man of letters"--engaged the services of two
skilled mechanics, Messieurs Joseph of Arras and J. Richard, who
constructed models of machines which ascended the atmosphere, carrying
t