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, for ampler confirmation, and clearer explication of this, let
us consider the present Figure, (which if I be not deceived, may
serve to detect the errors of some Practick Mechanitians who upon a
false foundation some times attempt impossible enterprizes,) in
which, unto the large Vessell E I D F, the narrow Funnell or Pipe I
C A B is continued, and suppose water infused into them, unto the
Levell L G H, which water shall rest in this position, not without
admiration in some, who cannot conceive how it can be, that the
heavie charge of the great Mass of water G D, pressing downwards,
should not elevate and repulse the little quantity of the other,
contained in the Funnell or Pipe C L, by which the descent of it is
resisted and hindered: But such wonder shall cease, if we begin to
suppose the water G D to be abased only to Q D, and shall
afterwards consider, what the water C L hath done, which to give
place to the other, which is descended from the Levell G H, to the
Levell Q O, shall of necessity have ascended in the same time, from
the Levell L unto A B. And the ascent L B, shall be so much greater
than the descent G Q, by how much the breadth of the Vessell G D,
is greater than that of the Funnell I C; which, in summe, is as
much as the water G D, is more than the water L C: but in regard
that the Moment of the Velocity of the Motion, in one Moveable,
compensates that of the Gravity of another what wonder is it, if
the swift ascent of the lesser Water C L, shall resist the slow
descent of the greater G D?_
The same, therefore, happens in this operation, as in rhe Stilliard,
in which a weight of two pounds counterpoyseth an other of 200,
asoften as that shall move in the same time, a space 100 times greater
than this: which falleth out when one Arme of the Beam is an hundred
times as long as the other. Let the erroneous opinion of those
therefore cease, who hold that a Ship is better, and easier born up in
a great abundance of water, then in a lesser quantity[13], (_this was
believed by_ Aristotle _in his Problems, Sect. 23, Probl. 2._) it being
on the contrary true, that its possible, that a Ship may as well float
in ten Tun of water, as in an Ocean.
[13] A ship flotes as well in ten Tun of Water as in an Ocean.
[Sidenote: A Solid specifiaclly graver than the water, cannot be
born up by any quantity of it.]
But following our matter, I say, that by what hath been hitherto
demonstrated, we may understand how, that
COROLLARY III.
_One of the above named Solids, when more grave_ in specie _than the
water, can never be sustained, by any whatever quantity of it._
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