Galilei, Galileo - Discourse concerning the natation of bodies

Galilei, Galileo, Discourse concerning the natation of bodies, 1663

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and, furthermore, not with every Matter, but with thoſe only,
wherewith it may be able ro execute the deſired operation. Like
as we ſee it verified by Experience, that the Acute and ſharp Angle is
more apt to cut, than the Obtuſe; yet alwaies provided, that both
the one and the other, be joyned with a Matter apt to cut, as for
example, with Steel. Therefore, a Knife with a fine and ſharp
edge, cuts Bread or Wood with much eaſe, which it will not do, if
the edge be blunt and thick: but he that will inſtead of Steel, take
Wax, and mould it into a Knife, undoubtedly ſhall never know the
effects of ſharp and blunt edges: becauſe neither of them will cut,
the Wax being unable by reaſon of its flexibility, to overcome the
hardneſs of the Wood and Bread. And, therefore, applying the
like diſcourſe to our purpoſe, they ſay, that the difference of Figure
will ſhew different effects, touching Natation and Submerſion, but
not conjoyned with any kind of Matter, but only with thoſe Matters
which, by their Gravity, are apt to reſiſt the Velocity of the water,
whence he that would elect for the Matter, Cork or other light wood
unable, through its Levity, to ſuperate the Craſſitude of the water,
and of that Matter ſhould forme Solids of divers Figures, woulld in
vain ſeek to find out what operation Figure hath in Natation or Sub
merſion; becauſe all would ſwim, and that not through any property
of this or that Figure, but through the debility of the Matter, want
ing ſo much Gravity, as is requiſite to ſuperate and overcome the
Denſity and Craſſitude of the water.

An objection a
gainſt the Expe
riment in Wax.

Its needfull, therefore, if wee would ſee the effect wrought by the
Diverſity of Figure, firſt to make choice of a Matter of its nature
apt to penetrate the Craſſitude of the water. And, for this effect,

they have made choice of ſuch a Matter, as fit, that being readily re
duced into Sphericall Figure, goes to the Bottom; and it is Ebony
of which they afterwards making a ſmall Board or Splinter, as thin as
a Lath, have illuſtrated how that this, put upon the Surface of the
water, reſts there without deſcending to the Bottom: and making, on
the otherſide, of the ſame wood a Ball, no leſs than a hazell Nut,
they ſhew, that this ſwims not, but deſcendes. From which Experi
ment, they think they may frankly conclude, that the Breadth ofthe
Figure in the flat Lath or Board, is the cauſe of its not deſcendingto
the Bottom, foraſmuch as a Ball of the ſame Matter, not different
from the Board in any thing but in Figure, ſubmergeth in the ſame
water to the Bottom. The diſcourſe and the Experiment hath really
ſo much of probability and likely hood of truth in it, that it would be
no wonder, if many perſwaded by a certain curſory obſervation,
ſhould yield credit to it; nevertheleſs, I think I am able to diſcover,
how that it is not free from falacy.

An Experi
ment in Ebany,
brought to diſ
prove the Expe
timent in Wax.

Beginning, therefore, to examine one by one, all the particulars that

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