Castelli, Benedetto, Of the mensuration of running waters, 1661

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              <s>
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              the variety of the velocities of the ſaid Water importeth, and the
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              knowledge of them is neceſſary to conclude the true quantity of
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              the running Water, we ſhall finde it manifeſt, that the benefit of
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              this Vent is far leſſe than it is generally thought: And mereover,
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              we ſhall finde, if I deceive not my ſelf, that there follow from
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              thence ſo many miſchiefs, that I could greatly incline to believe,
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              that it were more to the purpoſe wholly to ſtop it up, than to
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              maintain it open: yet I am not ſo wedded to my opinion, but
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              that I am ready to change my judgement upon ſtrength of better
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              reaſons; eſpecially of one that ſhall have firſt well underſtood
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              the beginning of this my diſcourſe, which I frequently inculcate,
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              becauſe its abſolutely impoſſible without this advertiſement to
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              treat of theſe matters, and not commit very great errours.</s>
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            <p type="main">
              <s>I propoſe therefore to conſideration, that although it be true,
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              that whilſt the water of the main P
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              o
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              is at its greateſt height, the
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              Bank and Dam then cut of the P
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              o
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              of
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              Ferara,
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              and the ſuperior
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              waters having a very great fall into the Channel of
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              Ferara,
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              they
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              precipitate into the ſame with great violence and velocity, and
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              with the ſame in the beginning, or little leſſe, they run towards
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              the P
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              o
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              of
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              Volana,
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              and of
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              Argenta
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              on the ſea coaſts; yet after the
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              ſpace of ſome few hours, the P
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              o
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              of
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              Ferara
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              being full, and the ſu­
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              perior Waters not finding ſo great a diclivity there, as they had
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              at the beginning of the cutting, they fall not into the ſame with
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              the former velocity, but with far leſſe, and thereby a great deal
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              leſſe Water begins to iſſue from the great P
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              o
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              ; and if we dili­
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              gently compare the velocity at the firſt cutting, with the velocity
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              of the Water after the cutting made, and when the P
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              o
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              of
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              Ferara
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              ſhall be full of Water, we ſhall finde perhaps that to be fifteen or
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              twenty times greater than this, and conſequently the Water
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              which iſſues from the great P
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              o,
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              that firſt impetuoſity being paſt,
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              ſhall be onely the fifteenth or twentieth part of that which iſſued
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              at the beginning; and therefore the Waters of the main P
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              o
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              will
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              return in a ſmall time almoſt to the firſt height. </s>
              <s>And here I will
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              pray thoſe who reſt not wholly ſatisfied with what hath been ſaid,
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              that for the love of truth, and the common good, they would
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              pleaſe to make diligent obſervation whether in the time of great
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              Floods, the ſaid Bank or Dam at
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              Bondeno
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              is cut, and that in few
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              hours the main P
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              o
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              diminiſheth, as hath been ſaid about a foot in
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              its height; that they would obſerve I ſay, whether, a day or two
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              being paſt, the Waters of the main P
                <emph type="italics"/>
              o
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              return almoſt to their firſt
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              height; for if this ſhould follow, it would be very clear, that the
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              benefit which reſulteth from this diverſion or Vent, is not ſo great
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              as is univerſally preſumed; I ſay, it is not ſo great as is
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              preſumed; becauſe, though it be granted for true, that
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              the Waters of the main P
                <emph type="italics"/>
              o,
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              abate at the beginning of </s>
            </p>
          </chap>
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      </text>
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