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

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              <s>
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              ed, the water put therein would be more preſſed and crowded.</s>
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            <p type="margin">
              <s>
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              * And as is at
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              large demonſtrated
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              by that moſt excel­
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              lent and lonour­
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              able perſonage Mr.
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                <emph type="italics"/>
              Botle
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              in the indu­
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              ſtrious experiment
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              of his Pneumatical
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              Engine.</s>
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            <p type="main">
              <s>And therefore, in our caſe, according to our principles we will
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              ſay, that the water of that Stream paſseth all under the ſaid
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              Bridge
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              Quattro-Capi,
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              for that being there moſt ſwift, it ought of
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              conſequence to be leſs in meaſure.</s>
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            <p type="main">
              <s>And here one may ſee, into how many errours a man may run
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              through ignorance of a true and real Principle, which once known
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              and well underſtood, takes away all miſts of doubting, and ea­
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              ſily reſolveth all difficulties.</s>
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            <p type="head">
              <s>
                <emph type="italics"/>
              COROLLARIE.
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              XII.</s>
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              <s>Through the ſame inadvertency of not regarding the variation
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              of velocity in the ſame Current, therea re committed by Ingi­
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              neers and Learned men, errours of very great moment (and I
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              could thereof produce examples, but for good reaſons I paſs
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              them over in ſilence) when they think, and propoſe, by deriving
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              new Channels from great Rivers, to diminiſh the meaſure of the
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              water in the River, and to diminiſh it proportionally, according
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              to the meaſure of the Water which they make to paſs through
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              the Channel, as making
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              v.g
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              a Channel fifty foot broad, in which
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              the derived water is to run waſte, ten foot deep, they think they
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              have diminiſhed the meaſure of the Water in the River five hun­
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              dred feet, which thing doth not indeed ſo fall out; and the rea­
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              ſon is plain; for that the Chanel being derived, the reſt of the
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              main River, diminiſheth in velocity, and therefore retains a grea­
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              ter meaſure than it had at firſt before the derivation of the Cha­
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              nel; and moreover, if the Chanel being derived, it ſhall not
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              conſerve the ſame velocity which it had at firſt in the main Ri­
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              ver, but ſhall diminiſh it, it will be neceſſary, that it hath a grea­
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              ter meaſure than it had before in the River; and therefore
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              to accompt aright, there ſhall not be ſo much water derived into
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              the Channel, as ſhall diminiſh the River, according to the quanti­
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              ty of the water in the Channel, as is pretended.</s>
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            <p type="head">
              <s>
                <emph type="italics"/>
              COROLLARIE
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              XIII.</s>
            </p>
            <p type="main">
              <s>This ſame conſideration giveth me occaſion to diſcover a moſt
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              ordinary errour, obſerved by me in the buſineſſe of the wa­
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              ter of
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              Ferara,
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              when I was in thoſe parts, in ſervice of the moſt
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              Reverend and Illuſtrious Monfignor
                <emph type="italics"/>
              Corſini
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              ; the ſublime wit of
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              whom hath been a very great help to me in theſe contemplations;
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              its very true, I have been much perplexed, whether I ſhould
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              commit this particular to paper, or paſſe it over in ſilence, for
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              that I have ever doubted, that the opinion ſo common and </s>
            </p>
          </chap>
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      </text>
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