1derſtood nothing at all, of that which others pretended full and
clearly to underſtand. And my doubt aroſe from my frequent
obſervation of many Trenches and Channels, which carry
water to turn Mills, in which Trenches, and Channels, the
water being meaſured, was found pretty deep; but if afterwards
the ſame water was meaſured in the fall it made to turn the
Wheel of the Mill, it was much leſſe, not amounting often to the
tenth part, nor ſometimes to the twentieth, inſomuch, that the
ſame running water came to be one while more, another while leſs
in meaſure, in divers parts of its Channel; and for that reaſon this
vulgar manner of meaſuring running Waters, as indeterminate and
uncertain, was by me juſtly ſuſpected, the meaſure being to be de
terminate, and the ſame. And here I freely confeſſe that I had fin
gular help to reſolve this difficulty from the excellent & accurate
way of diſcourſing, as in allother matters, ſo alſo in this, of the
Right Honourable and Truly Noble Signior Ciampoli, Secretary
of the Popes ſecret affairs. Who moreover, not ſparing ſor the coſts
of the ſame, generouſly gave me occaſion a few years paſt to try by
exact experiments that which paſt concerning this particular. And
to explain all more clearly with an example; we ſuppoſe a Veſſel
filled with Water, as for inſtance a Butt, which is kept full, though
ſtill water runneth out, and the Water run out by two Taps equal
of bigneſſe, one put in the bottom of the Veſſel, and the other in
the upper part; it is manifeſt that in the time wherein from the
upper part ſhall iſſue a determinate meaſure of water ſrom
the inferiour part there ſhall iſſue four, five, and many more of
the ſame meaſures, according to the difference of the height of
the Taps, and the diſtance of the upper Tap from the Superfici
es and level of the water of the Veſſel: and all this will alwayes
follow, though, as hath been ſaid, the Taps be equal, and the
water in diſcharging keep the ſaid Taps alwayes full. Where firſt
we note, that, although the meaſure of the Taps be equal, never
theleſſe there iſſueth from them in equal times unequal quantities
of water, And if we ſhould more attentively conſider this buſi
neſſe, we ſhould find, that the water by the lower Tap, run
neth and paſſeth with much greater velocity, then it doth by the
upper, whatever is the reaſon. If therefore we would have
ſuch a quantity of Water diſcharge from the upper tap, as
would diſcharge from the neather in the ſame time, it is plain, that
either the upper Taps muſt be multiplyed in ſuch ſort, that ſo
many more Taps in number be placed above than below, as the
neather tap ſhall be more ſwift than the upper, or the upper Tap
made ſo much bigger than the nether, by how much that be
neath ſhall be more ſwift than that above; and ſo then in equal
times, the ſame quantity of Water ſhall diſcharge from the upper,
as doth from the neather part.
clearly to underſtand. And my doubt aroſe from my frequent
obſervation of many Trenches and Channels, which carry
water to turn Mills, in which Trenches, and Channels, the
water being meaſured, was found pretty deep; but if afterwards
the ſame water was meaſured in the fall it made to turn the
Wheel of the Mill, it was much leſſe, not amounting often to the
tenth part, nor ſometimes to the twentieth, inſomuch, that the
ſame running water came to be one while more, another while leſs
in meaſure, in divers parts of its Channel; and for that reaſon this
vulgar manner of meaſuring running Waters, as indeterminate and
uncertain, was by me juſtly ſuſpected, the meaſure being to be de
terminate, and the ſame. And here I freely confeſſe that I had fin
gular help to reſolve this difficulty from the excellent & accurate
way of diſcourſing, as in allother matters, ſo alſo in this, of the
Right Honourable and Truly Noble Signior Ciampoli, Secretary
of the Popes ſecret affairs. Who moreover, not ſparing ſor the coſts
of the ſame, generouſly gave me occaſion a few years paſt to try by
exact experiments that which paſt concerning this particular. And
to explain all more clearly with an example; we ſuppoſe a Veſſel
filled with Water, as for inſtance a Butt, which is kept full, though
ſtill water runneth out, and the Water run out by two Taps equal
of bigneſſe, one put in the bottom of the Veſſel, and the other in
the upper part; it is manifeſt that in the time wherein from the
upper part ſhall iſſue a determinate meaſure of water ſrom
the inferiour part there ſhall iſſue four, five, and many more of
the ſame meaſures, according to the difference of the height of
the Taps, and the diſtance of the upper Tap from the Superfici
es and level of the water of the Veſſel: and all this will alwayes
follow, though, as hath been ſaid, the Taps be equal, and the
water in diſcharging keep the ſaid Taps alwayes full. Where firſt
we note, that, although the meaſure of the Taps be equal, never
theleſſe there iſſueth from them in equal times unequal quantities
of water, And if we ſhould more attentively conſider this buſi
neſſe, we ſhould find, that the water by the lower Tap, run
neth and paſſeth with much greater velocity, then it doth by the
upper, whatever is the reaſon. If therefore we would have
ſuch a quantity of Water diſcharge from the upper tap, as
would diſcharge from the neather in the ſame time, it is plain, that
either the upper Taps muſt be multiplyed in ſuch ſort, that ſo
many more Taps in number be placed above than below, as the
neather tap ſhall be more ſwift than the upper, or the upper Tap
made ſo much bigger than the nether, by how much that be
neath ſhall be more ſwift than that above; and ſo then in equal
times, the ſame quantity of Water ſhall diſcharge from the upper,
as doth from the neather part.
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