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 having seen how that the Moment wherewith such a Solid, as grave
_in specie_ as the water, contrasts with the Moment of any Mass of
water whatsoever, is able to retain it, even to its totall Submersion,
without its ever ascending; it remaineth, manifest, that the water is
far less able to raise it up, when it exceeds the same _in specie_:
so, that though you infuse water till its totall Submersion, it shall
still stay at the Bottome, and with such Gravity, and Resistance to
Elevation, as is the excess of its Absolute Gravity, above the
Absolute Gravity of a Mass equall to it, made of water, or of a Matter
_in specie_ equally grave with the water: and, though you should
moreover adde never so much water above the Levell of that which
equalizeth the Altitude of the Solid, it shall not, for all that,
encrease the Pression, or Gravitation, of the parts circumfused about
the said Solid, by which greater pression, it might come to be
repulsed; because, the Resistance is not made, but only by those parts
of the water, which at the Motion of the said Solid do also move, and
these are those only, which are comprehended by the two Superficies
equidistant to the Horizon, and their parallels, that comprehend the
Altitude of the Solid immerged in the water.
I conceive, I have by this time sufficiently declared and opened the
way to the contemplation of the true, intrinsecall and proper Causes
of diverse Motions, and of the Rest of many Solid Bodies in diverse
_Mediums_, and particularly in the water, shewing how all in effect,
depend on the mutuall excesses of the Gravity of the Moveables and of
the _Mediums_: and, that which did highly import, removing the
Objection, which peradventure would have begotten much doubting, and
scruple in some, about the verity of my Conclusion, namely, how that
notwithstanding, that the excess of the Gravity of the water, above
the Gravity of the Solid, demitted into it, be the cause of its
floating and rising from the Bottom to the Surface, yet a quantity of
water, that weighs not ten pounds, can raise a Solid that weighs above
100 pounds: in that we have demonstrated, That it sufficeth, that such
difference be found between the Specificall Gravities of the _Mediums_
and Moveables, let the particular and absolute Gravities be what they
will: insomuch, that a Solid, provided that it be Specifically less
grave than the water, although its absolute weight were 1000 pounds,
yet may it be born up and elevated by ten pounds of water, and less:
and on the contrary, another Solid, so that it be Specifically more
grave than the water, though in absolute Gravity it were not above a
pound, yet all the water in the Sea, cannot raise it from the Bottom,
or float it. This sufficeth me, for my present occasion, to have, by
the above declared Examples, discovered and demonstrated, without
extending such matters farther, and, as I might have done, into a long
Treatise: yea, but that there was a necessity of resolving the above
Public-domain text, read in full here on John Shaqi.
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