Alberti, Leone Battista, Architecture, 1755

List of thumbnails

< >
91
91 		92
92
93
93 		94
94
95
95 		96
96
97
97 		98
98
99
99 		100
100
< >
page |< < of 320 > >|
    <archimedes>
      <text>
        <body>
          <chap>
            <p type="main">
              <s>
                <pb xlink:href="003/01/093.jpg" pagenum="76"/>
              that the Buildings there did not joyn one to
                <lb/>
              ano her.
                <emph type="italics"/>
              Plato,
                <emph.end type="italics"/>
              on the contrary, is ſo far from
                <lb/>
              approving of thoſe Separations, that he would
                <lb/>
              have the Houſes all cloſe contiguous, and
                <lb/>
              that the joyning together of their Walls ſhould
                <lb/>
              make a Wall to the City.</s>
            </p>
            <p type="head">
              <s>CHAP. VI.</s>
            </p>
            <p type="head">
              <s>
                <emph type="italics"/>
              Of Bridges both of Wood and Stone, their proper Situation, their Peers,
                <lb/>
              Arches, Angles, Feet, Key-ſtones, Cramps, Pavements, and Slopes.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>The Bridge, no doubt, is a main Part
                <lb/>
              of the Street; nor is every Part of the
                <lb/>
              City proper for a Bridge; for beſides that it
                <lb/>
              is inconvenient to place it in a remote Corner
                <lb/>
              of the Town, where it can be of Uſe but to
                <lb/>
              few, and that it ought to be in the very Heart
                <lb/>
              of the City, to lie at hand for every body; it
                <lb/>
              ought certainly to be contrived in a Place
                <lb/>
              where it may eaſily be erected, and without
                <lb/>
              too great an Expence, and where it is likely
                <lb/>
              to be the moſt durable. </s>
              <s>We ſhould therefore
                <lb/>
              chuſe a Ford where the Water is not too deep;
                <lb/>
              where the Shore is not too ſteep; which is
                <lb/>
              not uncertain and moveable, but conſtant
                <lb/>
              and laſting. </s>
              <s>We ſhould avoid all Whirl­
                <lb/>
              pools, Eddies, Gulphs, and the like Inconve­
                <lb/>
              niences common in bad Rivers. </s>
              <s>We ſhould
                <lb/>
              alſo moſt carefully avoid all Elbows, where the
                <lb/>
              Water takes a Turn; for very many Reaſons;
                <lb/>
              the Banks in ſuch Places being very liable to
                <lb/>
              be broken, as we ſee by Experience, and be­
                <lb/>
              cauſe Pieces of Timber, Trunks of Trees, and
                <lb/>
              the like, brought down from the Country by
                <lb/>
              Storms and Floods, cannot ſwim down ſuch
                <lb/>
              Elbows in a ſtrait Line, but turn aſlant, meet
                <lb/>
              and hinder one another, and lodging againſt
                <lb/>
              the Piles grow into a great Heap, which ſtops
                <lb/>
              up the Arches, and with the additional
                <lb/>
              Weight of the Water at length quite breaks
                <lb/>
              them down.</s>
            </p>
            <p type="main">
              <s>OF Bridges, ſome are of Stone, others of
                <lb/>
              Wood. </s>
              <s>We ſhall ſpeak firſt of thoſe which
                <lb/>
              are of Wood, as the moſt eaſy of Execution;
                <lb/>
              next we ſhall treat of thoſe which are built of
                <lb/>
              Stone. </s>
              <s>Both ought to be as ſtrong as poſſible;
                <lb/>
              that therefore which is built of Wood, muſt
                <lb/>
              be fortified with a good Quantity of the
                <lb/>
                <arrow.to.target n="marg11"/>
                <lb/>
              ſtrongeſt Timbers. </s>
              <s>We cannot give a better
                <lb/>
              Example of this Sort of Bridges than that built
                <lb/>
              by
                <emph type="italics"/>
              fulius Cæſar,
                <emph.end type="italics"/>
              which he gives us a Deſcrip­
                <lb/>
              tion of himſelf, as follows: He faſtened to­
                <lb/>
              gether two Timbers, leaving a Diſtance be­
                <lb/>
              tween them of two Foot; their Length was
                <lb/>
              proportioned to the Depth of the River, and
                <lb/>
              they were a Foot and an half thick, and cut
                <lb/>
              ſharp at the Ends. </s>
              <s>Theſe he let down into
                <lb/>
              the River with Cranes, and drove them well in
                <lb/>
              with a Sort of Rammers, not perpendicularly
                <lb/>
              down like Piles, but ſlanting upwards, and
                <lb/>
              giving Way according to the Current of the
                <lb/>
              River. </s>
              <s>Then, oppoſite to theſe, he drove in
                <lb/>
              two others, faſtened together in the ſame Man­
                <lb/>
              ner, with a Diſtance between them at Bottom
                <lb/>
              of forty Foot, ſlanting contrary to the Force
                <lb/>
              and Current of the Stream. </s>
              <s>When theſe were
                <lb/>
              thus fixed, he laid acroſs from one to the other,
                <lb/>
              Beams of the Thickneſs of two Foot, which
                <lb/>
              was the Diſtance left between the Timbers
                <lb/>
              drove down; and faſtened theſe Beams at the
                <lb/>
              End, each with two Braces, which being
                <lb/>
              bound round and faſtened of oppoſite Sides,
                <lb/>
              the Strength of the whole Work was ſo great
                <lb/>
              and of ſuch a Nature, that the greatcr the
                <lb/>
              Force of Water was which bore againſt it,
                <lb/>
              the cloſer and firmer the Beams united. </s>
              <s>Over
                <lb/>
              theſe other Beams were laid acroſs and faſtened
                <lb/>
              to them, and a Floor, as we may call it, made
                <lb/>
              over them with Poles and Hurdles. </s>
              <s>At the
                <lb/>
              ſame Time, in the lower Part of the River,
                <lb/>
              below the Bridge, other Timbers, or ſloping
                <lb/>
              Piles, were driven down, which being faſtened
                <lb/>
              to the reſt of the Structure, ſhould be a Kind
                <lb/>
              of Buttreſs to reſiſt the Force of the Stream;
                <lb/>
              and other Piles were alſo driven in at a ſmall
                <lb/>
              Diſtance above the Bridge, and ſtanding ſome­
                <lb/>
              what above the Water, that if the Enemy
                <lb/>
              ſhould ſend Trunks of Trees, or Veſſels, down
                <lb/>
              the Stream, in order to break the Bridge, thoſe
                <lb/>
              Piles might receive and intercept their Vio­
                <lb/>
              lence, and prevent their doing any Prejudice
                <lb/>
              to the Work. </s>
              <s>All this we learn from
                <emph type="italics"/>
              Cæſar.
                <emph.end type="italics"/>
                <lb/>
              Nor is it foreign to our Purpoſe to take Notice
                <lb/>
              of what is practiced at
                <emph type="italics"/>
              Verona,
                <emph.end type="italics"/>
              where they
                <lb/>
              pave their wooden Bridges with Bars of Iron,
                <lb/>
              eſpecially where the Wheels of Carts and Wag­
                <lb/>
              gons are to paſs. </s>
              <s>It remains now that we
                <lb/>
              </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
Impressum