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. — John Shaqi
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
Let the Vessell be M L G N of any bigness, and let there be placed in
it the Solid Prisme D F G E, less grave _in specie_ than the water;
and look what proportion the Specificall Gravity of the water, hath to
that of the Prisme, such let the Altitude D F, have to the Altitude F
B. I say, that infusing water to the Altitude F B, the Solid D G shall
not float, but shall stand in _Equilibrium_, so, that that every
little quantity of water, that is infused, shall raise it. Let the
water, therefore, be infused to the Levell A B C; and; because the
Specifick Gravity of the Solid D G, is to the Specifick Gravity of the
water, as the altitude B F is to the altitude F D; that is, as the
Mass B G to the Mass G D; as the proportion of the Mass B G is to the
Mass G D, as the proportion of the Mass G D is to the Mass A F, they
compose the Proportion of the Mass B G to the Mass A F. Therefore, the
Mass B G is to the Mass A F, in a proportion compounded of the
proportions of the Specifick Gravity of the Solid G D, to the
Specifick Gravity of the water, and of the Mass G D to the Mass A F:
But the same proportions of the Specifick Gravity of G D, to the
Specifick Gravity of the water, and of the Mass G D to the Mass A F,
do also by the precedent _Lemma_, compound the proportion of the
absolute Gravity of the Solid D G, to the absolute Gravity of the Mass
of the water A F: Therefore, as the Mass B G is to the Mass A F, so is
the Absolute Gravity of the Solid D G, to the Absolute Gravity of the
Mass of the water A F. But as the Mass B G is to the Mass A F; so is
the Base of the Prisme D E, to the Surface of the water A B; and so is
the descent of the water A B, to the Elevation of the Prisme D G;
Therefore, the descent of the water is to the elevation of the Prisme,
as the absolute Gravity of the Prisme, is to the absolute Gravity of
the water: Therefore, the Moment resulting from the absolute Gravity
of the water A F, and the Velocity of the Motion of declination, with
which Moment it forceth the Prisme D G, to rise and ascend, is equall
to the Moment that results from the absolute Gravity of the Prisme D
G, and from the Velocity of the Motion, wherewith being raised, it
would ascend: with which Moment it resists its being raised: because,
therefore, such Moments are equall, there shall be an _Equilibrium_
between the water and the Solid. And, it is manifest, that putting a
little more water unto the other A F, it will increase the Gravity and
Moment, whereupon the Prisme D G, shall be overcome, and elevated till
that the only part B F remaines submerged. Which is that that was to
be demonstrated.
COROLLARY I.
[Sidenote: _H_ow far Solids less grave _in specie_ than water, do
submerge.]
_By what hath been demonstrated, it is manifest, that Solids less
grave_ in specie _than the water, submerge only so far, that as
much water in Mass, as is the part of the Solid submerged, doth
weigh absolutely as much as the whole Solid._
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