The Notebooks of Leonardo Da Vinci

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air would be dismembered or rent and broken up with the rending of
the air into which it was incorporated.

AS TO WHETHER THE SPIRIT, HAVING TAKEN THIS BODY OF AIR, CAN MOVE OF
ITSELF OR NOT.

It is impossible that the spirit infused into a certain quantity of
air, should move this air; and this is proved by the above passage
where it is said: the spirit rarefies that portion of the air in
which it incorporates itself; therefore this air will rise high
above the other air and there will be a motion of the air caused by
its lightness and not by a voluntary movement of the spirit, and if
this air is encountered by the wind, according to the 3rd of this,
the air will be moved by the wind and not by the spirit incorporated
in it.

AS TO WHETHER THE SPIRIT CAN SPEAK OR NOT.

In order to prove whether the spirit can speak or not, it is
necessary in the first place to define what a voice is and how it is
generated; and we will say that the voice is, as it were, the
movement of air in friction against a dense body, or a dense body in
friction against the air,--which is the same thing. And this
friction of the dense and the rare condenses the rare and causes
resistance; again, the rare, when in swift motion, and the rare in
slow motion condense each other when they come in contact and make a
noise and very great uproar; and the sound or murmur made by the
rare moving through the rare with only moderate swiftness, like a
great flame generating noises in the air; and the tremendous uproar
made by the rare mingling with the rare, and when that air which is
both swift and rare rushes into that which is itself rare and in
motion, it is like the flame of fire which issues from a big gun and
striking against the air; and again when a flame issues from the
cloud, there is a concussion in the air as the bolt is generated.
Therefore we may say that the spirit cannot produce a voice without
movement of the air, and air in it there is none, nor can it emit
what it has not; and if desires to move that air in which it is
incorporated, it is necessary that the spirit should multiply
itself, and that cannot multiply which has no quantity. And in the
4th place it is said that no rare body can move, if it has not a
stable spot, whence it may take its motion; much more is it so when
an element has to move within its own element, which does not move
of itself, excepting by uniform evaporation at the centre of the
thing evaporated; as occurs in a sponge squeezed in the hand held
under water; the water escapes in every direction with equal
movement through the openings between the fingers of the hand in
which it is squeezed.

As to whether the spirit has an articulate voice, and whether the
spirit can be heard, and what hearing is, and seeing; the wave of
the voice passes through the air as the images of objects pass to
the eye.

Nonentity.

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