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
For, if the Cylinder or Prisme M, less grave than the water, _v. gra._
in Subsequiteriall proportion, shall be put into the capacious Vessell
A B C D, and the water raised about it, to three quarters of its
height, namely, to its Levell A D: it shall be sustained and exactly
poysed in _Equilibrium_. The same will happen; if the Vessell E N S F
were very small, so, that between the Vessell and the Solid M, there
were but a very narrow space, and only capable of so much water, as
the hundredth part of the Mass M, by which it should be likewise
raised and erected, as before it had been elevated to three fourths of
the height of the Solid: which to many at the first sight, may seem a
notable Paradox, and beget a conceit, that the Demonstration of these
effects, were sophisticall and fallacious: but, for those who so
repute it, the Experiment is a means that may fully satisfie them. But
he that shall but comprehend of what Importance Velocity of Motion is,
and how it exactly compensates the defect and want of Gravity, will
cease to wonder, in considering that at the elevation of the Solid M,
the great Mass of water A B C D abateth very little, but the little
Mass of water E N S F decreaseth very much, and in an instant, as the
Solid M before did rise, howbeit for a very short space: Whereupon the
Moment, compounded of the small Absolute Gravity of the water E N S F,
and of its great Velocity in ebbing, equalizeth the Force and and
Moment, that results from the composition of the immense Gravity of
the water A B C D, with its great slownesse of ebbing; since that in
the Elevation of the Sollid M, the abasement of the lesser water E S,
is performed just so much more swiftly than the great Mass of water A
C, as this is more in Mass than that which we thus demonstrate.
[Sidenote: _T_he proportion according to which water riseth and
falls in different Vessels at the Immersion and Elevation of
Solids.]
In the rising of the Solid M, its elevation hath the same proportion
to the circumfused water E N S F, that the Surface of the said water,
hath to the Superficies or Base of the said Solid M; which Base hath
the same proportion to the Surface of the water A D, that the
abasement or ebbing of the water A C, hath to the rise or elevation of
the said Solid M. Therefore, by Perturbation of proportion, in the
ascent of the said Solid M, the abasement of the water A B C D, to the
abasement of the water E N S F, hath the same proportion, that the
Surface of the water E F, hath to the Surface of the water A D; that
is, that the whole Mass of the water E N S F, hath to the whole Mass A
B C D, being equally high: It is manifest, therefore, that in the
expulsion and elevation of the Solid M, the water E N S F shall exceed
in Velocity of _M_otion the water A B C D, asmuch as it on the other
side is exceeded by that in quantity: whereupon their Moments in such
operations, are mutually equall.
[Illustration]
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