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

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THEOREME. IX.
LEMMA II.

their Specificall Gravities, are equall in Abſolute
Gravities.
Solids whoſe
Maſſes are in
contrary pro­
portion to their
Specifick Gra­
vities, are equall
in abſolute Gra
vity.
Let A C and B be two Solids, and let the Maſs A C be to the
Maſs B, as the Specificall Gravity of the Solid B, is to the Speci­
ficall Gravity of the Solid A C: I ſay, the Solids A C and B are
equall in abſolute weight, that is, equally grave. For

[Figure 12]

if the Maſs A C be equall to the Maſs B, then, by the
Aſſumption, the Specificall Gravity of B, ſhall be
quall to the Specificall Gravity of A C, and being
quall in Maſs, and of the ſame Specificall Gravity they
ſhall abſolutely weigh one as much as another.
But
if their Maſſes ſhall be unequall, let the Maſs A C be greater, and in it
take the part C, equall to the Maſs B. And, becauſe the Maſſes B
and C are equall; the Abſolute weight of B, ſhall have the ſame pro­
portion to the Abſolute weight of C, that the Specificall Gravity of
B, hath to the Specificall Gravity of C; or of C A, which is the
ſame