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
Here I note, that the Conclusions of _Aristotle_ in generall are all
true, but methinks, that he applyeth them to particulars, in which
they have no place, as indeed they have in others, as for Example, Wax
is more easily divisible than Lead, and Lead than Silver, inasmuch as
Wax receives all the terms more easlier than Lead, and Lead than
Silver. Its true, moreover, that a little quantity of Silver is
easlier divided than a great Mass: and all these Propositions are
true, because true it is, that in Silver, Lead and Wax, there is
simply a Resistance against Division, and where there is the absolute,
there is also the respective. But if as well in water as in Air, there
be no Renitence against simple Division, how can we say, that the
water is easlier divided than the Air? We know not how to extricate
our selves from the Equivocation: whereupon I return to answer, that
Resistance of absolute Division is one thing, and Resistance of
Division made with such and such Velocity is another. But to produce
Rest, and to abate the Motion, the Resistance of absolute Division is
necessary; and the Resistance of speedy Division, causeth not Rest,
but slowness of Motion. But that as well in the Air, as in water,
there is no Resistance of simple Division, is manifest, for that there
is not found any Solid Body which divides not the Air, and also the
water: and that beaten Gold, or small dust, are not able to superate
the Resistance of the Air, is contrary to that which Experience shews
us, for we see Gold and Dust to go waving to and again in the Air, and
at last to descend downwards, and to do the same in the water, if it
be put therein, and separated from the Air. And, because, as I say,
neither the water, nor the Air do resist simple Division, it cannot be
said, that the water resists more than the Air. Nor let any object
unto me, the Example of most light Bodies, as a Feather, or a little
of the pith of Elder, or water-reed that divides the Air and not the
water, and from this infer, that the Air is easlier divisible than the
water; for I say unto them, that if they do well observe, they shall
see the same Body likewise divide the Continuity of the water[92], and
submerge in part, and in such a part, as that so much water in Mass
would weigh as much as the whole Solid. And if they shal yet persist
in their doubt, that such a Solid sinks not through inability to
divide the water, I will return them this reply, that if they put it
under water, and then let it go, they shall see it divide the water,
and presently ascend with no less celerity, than that with which it
divided the Air in descending: so that to say that this Solid ascends
in the Air, but that coming to the water, it ceaseth its Motion, and
therefore the water is more difficult to be divided, concludes
nothing: for I, on the contrary, will propose them a piece of Wood, or
of Wax, which riseth from the bottom of the water, and easily divides
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account