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

Table of figures

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              duſtry truly heroicall and admirable, by Monſignor
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              Maffei Bar­
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              herino,
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              then Prefect for the Wayes, and now Pope. </s>
              <s>And being
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              neceſſitated, that I might be able to walk in the Cave, and for
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              other cauſes, I let down the Sluices of the ſaid Cave, at the mouth
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              of the Lake: No ſooner were they ſtopt, but a great many of the
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              people of the Towns and Villages coaſting upon the
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              L
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              ake
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              flocking thither, began to make grievous complaints, that if thoſe
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              Sluices were kept ſhut, not onely the Lake would want its due
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              Vent, but alſo the parts adjacent to the Lake would be over
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              flown to their very great detriment. </s>
              <s>And becauſe at firſt appea­
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              rance their motion ſeemed very reaſonable, I found my ſelf hard
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              put to it, ſeeing no way to perſwade ſuch a multitude, that the
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              prejudice which they pretended I ſhould do them by keeping
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              the Sluices ſhut for two dayes, was abſolutely inſenſible; and that
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              by keeping them open, the Lake did not ebb in the ſame time ſo
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              much as the thickneſs of a ſheet of Paper: And therefore I was
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              neceſſitated to make uſe of the authority I had, and ſo followed
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              my buſineſs as cauſe required, without any regard to that Rab­
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              ble tumultuouſly aſſembled. </s>
              <s>Now when I am not working with
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              Mattock or Spade, but with the Pen and Diſcourſe, I intend to
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              demonſtrate clearly to thoſe that are capable of reaſon, and that
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              have well underſtood the ground of this my Treatiſe, that the
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              fear was altogether vain which thoſe people conceited. </s>
              <s>And
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              therefore I ſay, that the Emiſſary or Sluice of the Lake of
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              Peru­
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              gia,
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              ſtanding in the ſame mannner as at preſent, and the water
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              paſſing thorow it with the ſame velocity as now; to examine
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              how much the Lake may abate in two days ſpace, we ought to
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              conſider, what proportion the ſuperficies of the whole Lake hath
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              to the meaſure of the Section of the Emiſſary, and afterwards to
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              infer, that the velocity of the water by the Emiſſary or Sluice,
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              ſhall have the ſame proportion to the abatement of the Lake,
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              and to prove thorowly and clearly this diſcourſe, I intend to
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              demonſtrate the following Propoſition.</s>
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              <s>Suppoſe a Veſſel of any bigneſſe, and that it hath an Emiſſary
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              or Cock, by which it diſchargeth its water. </s>
              <s>And look what pro­
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              portion the ſuperſicies of the
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              veſſel hath to the meaſure of
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              the ſection of the cock, ſuch pro­
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              portion ſhall the velocity of the
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              Water in the Cock have to the
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              abatement of the Lake Let the
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              Veſſel be A B C D, H I L B, through which the Water runneth,
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              the ſuperficies of the Water in the Veſſel A D, and the ſection
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              of the Cock H L: and let the Water in the Veſſel
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              be ſuppoſed to have falne in one determinate time from A to F. </s>
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