Alberti, Leone Battista, Architecture, 1755

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              <s>
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              treat of the Stone-Bridge, the Parts whereof
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              are theſe: The Banks of the Shore, the Piers,
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              the Arches, and the Pavement. </s>
              <s>Between the
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              Banks of the Shore and the Piers, is this Diffe­
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              rence, that the Banks ought to be by much the
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              ſtrongeſt, inaſmuch as they are not only to ſup­
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              port the Weight of the Arches like the Piers,
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              but are alſo to bear the Foot of the Bridge, and
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              to bear againſt the Weight of the Arches, to
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              keep them from opening in any Part. </s>
              <s>We
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              ought therefore to be very careful in the Choice
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              of our Shore, and to find out, if poſſible, a
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              Rock of ſolid Stone, ſince nothing can be too
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              ſtrong that we are to intruſt with the Feet of
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              the Bridge; and as to the Piers, they muſt be
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              more or leſs numerous in Proportion to the
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              Breadth of the River. </s>
              <s>An odd Number of Ar­
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              ches is both moſt pleaſant to the Sight, and
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              conduces alſo to Strength; for the farther the
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              Current of the River lies from the Shore, the
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              freer it is from Impediment, and the freer
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              it is the ſwifter and eaſier it flows away;
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              for this therefore we ought to leave a Paſſage
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              perfectly free and open, that it may not ſhake
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              and prejudice the Piers by ſtruggling with the
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              Reſiſtance which it meets with from them.
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              </s>
              <s>The Piers ought to be placed in thoſe Parts of
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              the River, where the Water flows the moſt
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              ſlowly, and (to uſe ſuch an Expreſſion) the
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              moſt lazily: And thoſe Parts you may eaſily
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              find out by means of the Tides: Otherwiſe
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              you may diſcover them in the following Man­
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              ner: Imitate thoſe who threw Nuts into a
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              River, whereby the Inhabitants of a Town be­
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              ſieged, gathering them up, were preſerved
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              from ſtarving; ſtrew the whole Breadth of the
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              River, about fifteen hundred Paces above the
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              Place which you intend for your Bridge, and
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              eſpecially when the River is fulleſt, with ſome
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              ſuch light Stuff that will eaſily float: And in
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              thoſe Places where the Things you have
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              thrown in Cluſters thickeſt together, you may
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              be ſure the Current is ſtrongeſt. </s>
              <s>In the Situ­
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              ation of your Piers therefore avoid thoſe Places,
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              and chuſe thoſe others to which the Things
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              you throw in come the ſloweſt and thinneſt.</s>
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              <s>KING
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              Mina,
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              when he intended to build the
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              Bridge of
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              Memphis,
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              turned the
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              Nile
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              out of its
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              Channel, and carried it another Way among
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              ſome Hills, and when he had finiſhed his Build­
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              ing brought it back again into its old Bed.
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                <emph type="italics"/>
              Nicore
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              Queen of the
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              Aſſyrians,
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              having pre­
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              pared all the Materials for building a Bridge,
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              dug a great Lake, and into that turned the
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              River; and as the Channel grew dry as the
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              Lake filled, ſhe took that Time to build her
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              Piers. </s>
              <s>Theſe mighty Things were done by
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              thoſe great Princes: As for us, we are to pro­
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              ceed in the following Manner: Make the
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              Foundations of your Piers in Autumn, when
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              the Water is loweſt, having firſt raiſed an In­
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              cloſure to keep off the Water, which you may
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              do in this Manner: Drive in a double Row of
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              Stakes, very cloſe and thick ſet, with their
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              Heads above the Top of the Water, like a
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              Trench; then put Hurdles within this double
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              Row of Stakes, cloſe to that Side of the Row
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              which is next the intended Pier, and fill up
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              the Hollow between the two Rows with Ruſhes
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              and Mud, ramming them together ſo hard
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              that no Water can poſſibly get through. </s>
              <s>Then
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              whatever you find within this Incloſure, Water,
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              Mud, Sand, and whatever elſe is a Hindrance
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              to you, throw out. </s>
              <s>For the reſt of your Work,
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              you muſt obſerve the Rules we have laid down
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              in the preceding Book. </s>
              <s>Dig till you come to
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              a ſolid Foundation, or rather make one of
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              Piles burnt at the End, and driven in as cloſe
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              together as ever they can ſtick. </s>
              <s>And here I
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              have obſerved that the beſt Architects uſed to
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              make a continued Foundation of the whole
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              Length of the Bridge, and not only under each
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              Pier; and this they did, not by ſhutting out
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              the whole River at once by one ſingle Inclo­
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              ſure, but by firſt making one Part, then another,
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              and ſo joyning the whole together by degrees;
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              for it would be impoſſible to withſtand and
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              repulſe the whole Force of the Water at once;
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              we muſt therefore, while we are at work with
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              one Part, leave another Part open, for a Paſ­
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              ſage for the Stream.</s>
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              <s>YOU may leave theſe Paſſages either in the
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              Channel itſelf, or if you think it more conve­
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              nient, you may frame wooden Dams, or hang­
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              ing Channels, by which the ſuperfluous Wa­
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              ter may run off. </s>
              <s>But if you find the Expence
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              of a continued Foundation for the whole Bridge
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              too great, you may only make a ſeparate Foun­
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              dation for every particular Pier, in the Form
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              of a Ship with one Angle in the Stern, and an­
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              other in the Head, lying directly even with the
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              Current of the Water, that the Force of the
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              Water may be broken by the Angle. </s>
              <s>We are
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              to remember that the Water is much more
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              dangerous to the Stern, than to the Head of
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              the Piers, which appears from this, that at
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              the Stern the Water is in a more violent Mo­
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              tion than at the Head, and forms Eddies,
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              which turn up the Ground at the Bottom;
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              while the Head ſtands firm and ſafe, being
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              guarded and defended by the Banks of Sand
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              thrown up before it by the Channel. </s>
              <s>Now </s>
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