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

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1or theſe others, a ſimple negation, or privation, ſuch as Vacuity

would be in reference to Repletion, argueth againſt Democritus and
ſaith: If it be true, as you ſuppoſe, then there ſhall be a great Maſs
of water, which ſhall have more of Fire, than a ſmall Maſs of Air,
and a great Maſs of Air, which ſhall have more of Earth than a
tle Maſs of water, whereby it would enſue, that a great Maſs of Air,
ſhould come more ſwiftly downwards, than a little quantity of
water: But that is never in any caſe ſoever: Therefore Democritus
diſcourſeth erroneouſly.
Ariſtotle ſhews
his deſire of
finding
critus in an
ror, to exceed
that of
veting Truth.
Cap. 5. Text 41.
Id. ibid.
But in my opinion, the Doctrine of Democritus, is not by this
gation overthrown, but if I erre not, the manner of Ariſtotle deduction
either concludes not, or if it do conclude any thing, it may with
quall force be reſtored againſt himſelf. Democritus will grant to
Ariſtotle, that there may be a great Maſs of Air taken, which
tains more Earth, than a ſmall quantity of water, but yet will deny,
that ſuch a Maſs of Air, ſhall go faſter downwards than a little water,
and that for many reaſons.
Firſt, becauſe if the greater quantity
of Earth, contained in the great Maſs of Air, ought to cauſe a greater
Velocity than a leſs quantity of Earth, contained in a little quantity
of water, it would be neceſſary, firſt, that it were true, that a
greater Maſs of pure Earth, ſhould move more ſwiftly than a leſs:
But this is falſe, though Ariſtotle in many places affirms it to be true:
becauſe not the greater abſolute, but the greater ſpecificall Gravity,

is the cauſe of greater Velocity: nor doth a Ball of Wood,
ing ten pounds, deſcend more ſwiftly than one weighing ten Ounces,
and that is of the ſame Matter: but indeed a Bullet of Lead of four
Ounces, deſcendeth more ſwiftly than a Ball of Wood of twenty
Pounds: becauſe the Lead is more grave in ſpecie than the Wood.
Therefore, its not neceſſary, that a great Maſs of Air, by reaſon of
the much Earth contained in it, do deſcend more ſwiftly than a little

Maſs of water, but on the contrary, any whatſoever Maſs of water,
ſhall move more ſwiftly than any other of Air, by reaſon the
pation of the terrene parts in ſpecie is greater in the water, than in the
Air.
Let us note, in the ſecond place, how that in multiplying the
Maſs of the Air, we not only multiply that which is therein of terrene,
but its Fire alſo: whence the Cauſe of aſcending, no leſs encreaſeth,
by vertue of the Fire, than that of deſcending on the account of its
multiplied Earth.
It was requiſite in increaſing the greatneſs of the
Air, to multiply that which it hath of terrene only, leaving its Fire
in its firſt ſtate, for then the terrene parts of the augmented Air,
overcoming the terrene parts of the ſmall quantity of water, it might
with more probability have been pretended, that the great
ty of Air, ought to deſcend with a greater Impetus, than the little
quantity of water.

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