A Discourse Presented to the Most Serene Don Cosimo II., Great Duke of Tuscany, Concerning the Natation of Bodies Vpon, and Submersion In, the Water.Galilei, Galileo
Science
A Discourse Presented to the Most Serene Don Cosimo II., Great Duke of Tuscany, Concerning the Natation of Bodies Vpon, and Submersion In, the Water.
Galilei, Galileo
Hydrostatics; Specific gravity
In
consequence of this that hath been demonstrated, sundry and various
Conclusions may be gathered, by which the truth of my principall
Proposition comes to be more and more confirmed, and the imperfection
of all former Argumentations touching the present Question cometh to
be discovered.
_And first we gather from the things demonstrated, that,_
THEOREME VII.
[Sidenote: The heaviest Bodies may swimme.]
_All Matters, how heavy soever, even to Gold it self, the heaviest
of all Bodies, known by us, may float upon the Water._
Because its Gravity being considered to be almost twenty times greater
than that of the water, and, moreover, the greatest Altitude that the
Rampart of water can be extended to, without breaking the Contiguity
of the Air, adherent to the Surface of the Solid, that is put upon the
water being predetermined, if we should make a Plate of Gold so thin,
that it exceeds not the nineteenth part of the Altitude of the said
Rampart, this put lightly upon the water shall rest, without going to
the bottom: and if Ebony shall chance to be in sesquiseptimall
proportion more grave than the water, the greatest thickness that can
be allowed to a Board of Ebony, so that it may be able to stay above
water without sinking, would be seaven times more than the height of
the Rampart Tinn, _v. gr._ eight times more grave than water, shall
swimm as oft as the thickness of its Plate, exceeds not the 7th part
of the Altitude of the Rampart.
[Sidenote: _He elsewhere cites this as a Proposition, therefore I
make it of that number._]
And here I will not omit to note, as a second Corrollary dependent
upon the things demonstrated, that,
THEOREME VIII.
[Sidenote: Natation and Submersion, collected from the thickness,
excluding the length and breadth of Plates.]
_The Expansion of Figure not only is not the Cause of the Natation
of those grave Bodies, which otherwise do submerge, but also the
determining what be those Boards of Ebony, or Plates of Iron or
Gold that will swimme, depends not on it, rather that same
determination is to be collected from the only thickness of those
Figures of Ebony or Gold, wholly excluding the consideration of
length and breadth, as having no wayes any share in this Effect._
It hath already been manifested, that the only cause of the Natation
of the said Plates, is the reduction of them to be less grave than the
water, by means of the connexion of that Air, which descendeth
together with them, and possesseth place in the water; which place so
occupyed, if before the circumfused water diffuseth it self to fill
it, it be capable of as much water, as shall weigh equall with the
Plate, the Plate shall remain suspended, and sinke no farther.
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