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
Nay, I will say more, that if we shall consider Gold in comparison of
water, we shall find, that it exceeds it in Gravity almost twenty
times, so that the Force and Impetus, wherewith a Ball of Gold goes to
the Bottom, is very great. On the contrary, there want not matters, as
Virgins Wax, and some Woods, which are not above a fiftieth part less
grave than water, whereupon their Ascension therein is very slow, and
a thousand times weaker than the _Impetus_ of the Golds descent: yet
notwithstanding, a plate of Gold swims without descending to the
Bottom, and, on the contrary, we cannot make a Cake of Wax, or thin
Board of Wood, which put in the Bottom of the Water, shall rest there
without ascending. Now if the Figure can obstruct the Penetration, and
impede the descent of Gold, that hath so great an _Impetus_, how can
it choose but suffice to resist the same Penetration of the other
matter in ascending, when as it hath scarce a thousandth part of the
_Impetus_ that the Gold hath in descending? Its therefore, necessary,
that that which suspends the thin Plate of Gold, or Board of Ebony,
upon the water, be some thing that is wanting to the other Cakes and
Boards of Matters less grave than the water; since that being put to
the Bottom, and left at liberty, they rise up to the Surface, without
any obstruction: But they want not for flatness and breadth of Figure:
Therefore, the spaciousnesse of the Figure, is not that which makes
the Gold and Ebony to swim.
And, because, that the excess of their Gravity above the Gravity of
the water, is questionless the Cause of the sinking of the flat piece
of Ebony, and the thin Plate of Gold, when they go to the Bottom,
therefore, of necessity, when they float, the Cause of their staying
above water, proceeds from Levity, which in that case, by some
Accident, peradventure not hitherto observed, cometh to meet with the
said Board, rendering it no longer as it was before, whilst it did
sink more ponderous than the water, but less.
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