Galilei, Galileo - Discourse concerning the natation of bodies

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

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ties departing, if it ſhall be more grave in ſpecie than Water, fil but its
Poroſities with Water, and you ſhal have a Compoſt of Water and
of Wood more grave than Water, but not by vertue of the Water re
ceived into and imbibed by the Poroſities, but of that Matter of the
Wood which remains when the Air is departed: and being ſuch it
ſhall, according to the Doctrine of Archimedes, goe to the bottom,
like as before, according to the ſame Doctrine it did ſwim.

T he Authors an
ſwer to the third
Objection.

As to that finally which preſents it ſelf in the fourth place, namely,

that the Ancients have been heretofore confuted by Ariſtotle, who
denying Poſitive and Abſolute Levity, and truely eſteeming all Bo
dies to be grave, ſaid, that that which moved upward was driven by
the circumambient Air, and therefore that alſo the Doctrine of
Archimedes, as an adherent to ſuch an Opinion was con
victed and confuted: I anſwer firſt, that Signor Buonamico in my
judgement hath impoſed upon Archimedes, and deduced from his
words more than ever he intended by them, or may from his Propo
ſitions be collected, in regard that Archimedes neither denies, nor ad
mitteth Poſitive Levity, nor doth he ſo much as mention it: ſo that
much leſs ought Buonamico to inferre, that he hath denyed that it
might be the Cauſe and Principle of the Aſcenſion of Fire, and other
Light Bodies: having but only demonſtrated, that Solid Bodies

more grave than Water deſcend in it, according to the exceſs of their
Gravity above the Gravity of that, he demonſtrates likewiſe, how the

leſs grave aſcend in the ſame Water, accordng to its exceſs of Gra
ty, above the Gravity of them. So that the moſt that can be gather
ed from the Dem onſtration of Archimedes is, that like as the exceſs
of the Gravity of the Moveable above the Gravity of the Water, is
the Cauſe that it deſcends therein, ſo the exceſs of the Gravity of
the water above that of the Moveable, is a ſufficient Cauſe why it deſ
cends not, but rather betakes it ſelf to ſwim: not enquiring whe
ther of moving upwards there is, or is not any other Cauſe contrary
to Gravity: nor doth Archimedes diſcourſe leſs properly than if one
ſhould ſay: If the South Winde ſhall aſſault the Barke with greater
Impetus than is the violence with which the Streame of the River car
ries it towards the South, the motion of it ſhall be towards the North:
but if the Impetus of the Water ſhall overcome that of the Winde, its
motion ſhall be towards the South. The diſcourſe is excellent and
would be unworthily contradicted by ſuch as ſhould oppoſe it, ſaying:
Thou miſ-alledgeſt as Cauſe of the motion of the Bark towards the
South, the Impetus of the Stream of the Water above that of the
South Winde; miſ-alledgeſt I ſay, for it is the Force of the North
Winde oppoſite to the South, that is able to drive the Bark towards
the South. Such an Objection would be ſuperfluous, becauſe he which
alledgeth for Cauſe of the Motion the ſtream of the Water, denies not

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