Alberti, Leone Battista, Architecture, 1755

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              <s>
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              order to break the Fury of the Waves, that
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              not finding any Thing to beat againſt
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              with their whole Strength, they may fall back
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              gently and not with too violent a Precipitation.
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              </s>
              <s>Thus the Wave which is upon Return will
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              meet that which is coming on, and deaden its
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              Force. </s>
              <s>The Mouths of Rivers ſeem to be of
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              the ſame Nature with the Port, as they afford
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              Shelter to Veſſels againſt Storms. </s>
              <s>They ought
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              therefore to be fortified and made narrower to
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              exclude the Fury of the Sea.
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              Propertius
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              ſays,</s>
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              <s>
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              Reſolve to conquer or be o'ercome,
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              This is the Wheel of Love
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              —</s>
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              <s>IT is the ſame in this Caſe; for the Mouths
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              of Rivers by the inceſſant Attacks of the Sea
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              are either overcome and filled up with Sand;
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              or elſe by a conſtant and obſtinate Reſiſtance,
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              they conquer and keep their Paſſages clear.
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              </s>
              <s>For this Reaſon it is an admirable Method to
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              open the River a double Diſcharge into the
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              Sea by two different Branches, if you have but
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              Water enough to ſupply them; not only that
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              Ships may be able to get in at one of them,
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              though the Wind be contrary for the other;
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              but alſo that if one of them be ſtopt up, either
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              by ſome Storm at Sea, or by ſome ſtrong
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              Wind blowing into it, in ſuch a Manner that
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              the Land-floods would be driven back again
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              into the Country, they may have another Paſſ­
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              age open to diſcharge themſelves into the Sea.
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              </s>
              <s>But of this enough. </s>
              <s>The next Point is how
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              to clean a River.
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              Cæſar
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              took a great deal of
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              Care about cleaning the
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              Tyber,
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              which was ſtopt
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              up with Rubbiſh, and there are vaſt Heaps of
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              the Stuff that was taken out ſtill to be ſeen not
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              far from the River, as well within the City as
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              without. </s>
              <s>By what Methods he got ſo much
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              Rubbiſh out of ſo ſwift a River, I do not re­
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              member to have read: But I ſuppoſe he made
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              uſe of Frames to ſhut out the River and then
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              emptying the Water out of them, he might
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              eaſily take out the Rubbiſh. </s>
              <s>Theſe Frames
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              are made in the following Manner: Prepare
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              ſome ſtrong Timbers cut ſquare, with Grooves
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              cut in the Sides of them from Top to Bottom
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              four Inches deep, and in Breadth equal to the
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              Thickneſs of the Planks which you intend to
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              uſe in this Work; and prepare your Planks al­
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              ſo of equal Length and Thickneſs with one
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              another. </s>
              <s>Having got theſe Things ready,
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              drive down your Timbers ſo as they may ſtand
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              perpendicular, at Diſtances from each other
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              equal to the Length of your Planks. </s>
              <s>When
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              your Timbers are well fixed, let your Planks
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              into the Grooves and drive them down to the
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              Bottom. </s>
              <s>Our Workmen call theſe Frames
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              Cataracts. </s>
              <s>Go on in the ſame Manner to fill
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              up the Spaces between the Timbers with Planks
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              and drive them as cloſe together as poſſible.
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              </s>
              <s>Then go to work immediately with your
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              Pumps, Syphons, Buckets and all your other
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              Implements for emptying out the Water, put­
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              ting on as many Hands as you can, and labour­
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              ing without Intermiſſion till you have thrown
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              out all the Water within your Incloſure. </s>
              <s>If it
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              leaks in any Part, ſtop up the Crack with any
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              old Rags: And thus the Buſineſs may be done.
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              </s>
              <s>Between this Frame and that which we men­
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              tioned as neceſſary in the Building of Bridges,
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              there is this Difference; that the latter muſt be
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              ſtable and laſting, being to ſtand not only till
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              the Piers are built, but even till the Super­
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              ſtructure is ſettled; whereas this is only tem­
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              porary, and as ſoon as the Dirt is got out to be
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              preſently removed to another Place. </s>
              <s>But I
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              adviſe you, whether you clean your River by
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              the Help of this Frame, or by turning the
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              Courſe of the Water, that you do not pretend
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              to ſtrive againſt the whole Force of the Stream
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              at a Time in any one Place, but go on Step by
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              Step and by Degrees. </s>
              <s>All Works raiſed againſt
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              the Violence of Waters, if they are made in
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              the Form of Arches, with their Backs turned
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              againſt the Weight of the Water, they will be
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              able to make the ſtouter Reſiſtance. </s>
              <s>You may
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              level a Torrent or Water-fall by laying a Bar­
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              rier acroſs the Stream in ſuch a Manner that the
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              Water is obliged to riſe a good deal higher
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              than uſual: For the Water running over from
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              the Top of this Barrier, will dig up the Ridge
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              in the Channel by its fall; and then even the
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              Channel above the Torrent, quite to the Spring
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              will be levelled in Proportion to the lower
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              Part of the Channel; for the Water in its De­
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              ſcent will be continually moving and carrying
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              away the Earth. </s>
              <s>You may clean your Chan­
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              nel by turning Oxen into it in the following
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              Manner: Stop it up that the Water may ſwell;
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              then drive your Cattle about in it ſo that they
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              may diſturb all the Mud, and then opening the
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              Stream that the Water may pour in rapidly, it
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              will waſh and carry away all the Dirt. </s>
              <s>If any
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              thing lies buried and fixed in the Stream ſo as
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              to ſpoil the Navigation, beſides the common
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              Machines uſed by Workmen for removing ſuch
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              Obſtructions, it is a very good Method to load
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              a Barge deep, and to it faſten with Ropes the
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              Impediment which you would pull up: Then </s>
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