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
And he that would have a more easie Experiment, let him take two
Cylinders of the same Matter, one long and small, and the other short,
but very broad, and let him put them in the water, not distended, but
erect and endways: he shall see, if he diligently measure the parts of
the one and of the other, that in each of them the part submerged,
retains exactly the same proportion to that out of the water, and that
no greater part is submerged of that long and small one, than of the
other more spacious and broad: howbeit, this rests upon a very large,
and that upon a very little Superficies of water: therefore the
diversity of Figure, occasioneth neither facility, nor difficulty, in
parting and penetrating the Continuity of the water, and,
consequently, cannot be the Cause of the Natation or Submersion. He
may likewise discover the non operating of variety of Figures, in
arising from the Bottom of the water, towards the Surface, by taking
Wax, and tempering it with a competent quantity of the filings of
Lead, so that it may become a considerable matter graver than the
water: then let him make it into a Ball, and thrust it unto the Bottom
of the water; and fasten to it as much Cork, or other light matter, as
just serveth to raise it, and draw it towards the Surface: for
afterwards changing the same Wax into a thin Cake, or into any other
Figure, that same Cork shall raise it in the same manner to a hair.
This silenceth not my Antagonists, but they say, that all the
discourse hitherto made by me little importeth to them, and that it
serves their turn, that they have demonstrated in one only particular,
and in what matter, and under what Figure pleaseth them, namely, in a
Board and in a Ball of Ebony, that this put in the water, descends to
the Bottom, and that stays atop to swim: and the Matter being the
same, and the two Bodies differing in nothing but in Figure, they
affirm, that they have with all perspicuity demonstrated and sensibly
manifested what they undertook; and lastly, that they have obtained
their intent. Nevertheless, I believe, and thinke, I can demonstrate,
that that same Experiment proveth nothing against my Conclusion.
[Sidenote: In Experiments of Natation, the Solid is to be put
into, not upon the water.]
And first, it is false, that the Ball descends, and the Board not: for
the Board shall also descend, if you do to both the Figures, as the
words of our Question requireth; that is, if you put them both into
the water.
[Sidenote: The Question of Natation stated.]
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