Galilei, Galileo, Discourse concerning the natation of bodies, 1663

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1that without them would go to the bottom: Of which two Pofitions,
I eſteem the ſecond to be true, underſtanding it of water, conſtituted
in its naturall Coldneſs.
But if we take a Veſſel of Glaſs, or Braſs,
or any other hard matter, full of cold water, within which is put a
Solid of a flat or concave Figure, but that in Gravity exceeds the
water ſo little, that it goes ſlowly to the bottom; I ſay, that putting
ſome burning Coals under the ſaid Veſſel, as ſoon as the new Fiery
Atomes ſhall have penetrated the ſubſtance of the Veſſel, they ſhall
without doubt, aſcend through that of the water, and thruſting
gainſt the foreſaid Solid, they ſhall drive it to the Superficies, and
there detain it, as long as the incurſions of the ſaid Corpuſcles ſhall
laſt, which ceaſing after the removall of the Fire, the Solid being
bandoned by its ſupporters, ſhall return to the bottom.
Democritus
futed by the
Authour.
But Democritus notes, that this Caufe only takes place when we
treat of raiſing and ſuſtaining of Plates of Matters, but very little
heavier than the water, or extreamly thin: but in Matters very
grave, and of ſome thickneſs, as Plates of Lead or other Mettal, that
ſame Effect wholly ceaſeth: In Teſtimony of which, let's obſerve
that ſuch Plates, being raiſed by the Fiery Atomes, aſcend through
all the depth of the water, and ſtop at the Confines of the Air, ſtill
ſtaying under water: but the Plates of the Opponents ſtay not, but
only when they have their upper Superficies dry, nor is there any
means to be uſed, that when they are within the water, they may
not ſink to the bottom.
The cauſe, therefore, of the Supernatation
of the things of which Democritus ſpeaks is one, and that of the
natation of the things of which we ſpeak is another.
But, returning

to Ariſtotle, methinks that he hath more weakly confuted Democritus,
than Democritus himſelf hath done: For Ariſtotle having propounded
the Objection which he maketh againſt him, and oppoſed him with
ſaying, that if the calid aſcendent Corpuſcles were thoſe that raiſed
the thin Plate, much more then would ſuch a Solid be raiſed and
born upwards through the Air, it ſheweth that the deſire in Ariſtotle
to detect Democritus, was predominate over the exquiſiteneſs of Solid
Philoſophizing: which deſire of his he hath diſcovered in other
caſions, and that we may not digreſs too far from this place, in the
Text precedent to this Chapter which we have in hand; where he

attempts to confute the ſame Democritus, for that he, not
ing himſelf with names only, had eſſayed more particularly to
clare what things Gravity and Levity were; that is, the Cauſes of
deſcending and aſcending, (and had introduced Repletion and
cuity) aſcribing this to Fire, by which it moves upwards, and that to
the Earth, by which it deſcends; afterwards attributing to the
Air more of Fire, and to the water more of Earth.
But Ariſtotle
deſiring a poſitive Cauſe, even of aſcending Motion, and not as Plato,

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